Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.094405
M. Riepp, A. Philippi-Kobs, L. Müller, W. Roseker, R. Rysov, R. Frömter, K. Bagschik, M. Hennes, D. Gupta, S. Marotzke, M. Walther, S. Bajt, R. Pan, T. Golz, N. Stojanovic, C. Boeglin, G. Grübel
The controlled manipulation of spins on ultrashort timescales is among the most promising solutions for novel high-speed and low-power-consumption spintronic and magnetic recording applications. To do so, terahertz (THz) light pulses can be used to drive coherent magnetization dynamics in ferromagnetic thin films. We were able to resolve these dynamics on the nanoscale employing THz-pump x-ray resonant magnetic scattering from the labyrinth-type domain network of a Co/Pt multilayer with perpendicular magnetic anisotropy. Our results reveal THz-driven ultrafast demagnetization as well as coherent local magnetization oscillations at the THz fundamental frequency of . We observe a temporal lag between femtosecond demagnetization and the start of the coherent magnetization oscillations that can be understood by a time-dependent damping. The dynamics of the domain and domain-wall contributions are found to be highly correlated, suggesting the applicability of THz spin control in magnetic nanostructures.
在超短时间尺度上可控地操纵自旋是新型高速、低功耗自旋电子和磁记录应用最有前途的解决方案之一。为此，太赫兹（THz）光脉冲可用于驱动铁磁薄膜中的相干磁化动力学。我们利用太赫兹泵浦 X 射线共振磁散射，从具有垂直磁各向异性的 Co/Pt 多层迷宫式畴网络中解析了这些纳米级动态。我们的研究结果表明，在 2.5THz 的太赫兹基频上，存在太赫兹驱动的超快退磁和相干局部磁化振荡。我们观察到飞秒退磁与相干磁化振荡开始之间存在时间差，这可以通过随时间变化的阻尼来理解。我们发现畴和畴壁的动态贡献是高度相关的，这表明太赫兹自旋控制适用于磁性纳米结构。
{"title":"Terahertz-driven coherent magnetization dynamics in labyrinth-type domain networks","authors":"M. Riepp, A. Philippi-Kobs, L. Müller, W. Roseker, R. Rysov, R. Frömter, K. Bagschik, M. Hennes, D. Gupta, S. Marotzke, M. Walther, S. Bajt, R. Pan, T. Golz, N. Stojanovic, C. Boeglin, G. Grübel","doi":"10.1103/physrevb.110.094405","DOIUrl":"https://doi.org/10.1103/physrevb.110.094405","url":null,"abstract":"The controlled manipulation of spins on ultrashort timescales is among the most promising solutions for novel high-speed and low-power-consumption spintronic and magnetic recording applications. To do so, terahertz (THz) light pulses can be used to drive coherent magnetization dynamics in ferromagnetic thin films. We were able to resolve these dynamics on the nanoscale employing THz-pump x-ray resonant magnetic scattering from the labyrinth-type domain network of a Co/Pt multilayer with perpendicular magnetic anisotropy. Our results reveal THz-driven ultrafast demagnetization as well as coherent local magnetization oscillations at the THz fundamental frequency of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>2.5</mn><mspace width=\"0.16em\"></mspace><mi>THz</mi></mrow></math>. We observe a temporal lag between femtosecond demagnetization and the start of the coherent magnetization oscillations that can be understood by a time-dependent damping. The dynamics of the domain and domain-wall contributions are found to be highly correlated, suggesting the applicability of THz spin control in magnetic nanostructures.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.094501
Alex Gurevich, Ahmad Sheikhzada
We report numerical simulations of coupled sine-Gordon and heat diffusion equations describing dynamic states stimulated by a trapped vortex driven by dc current in a stack of up to <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>N</mi><mo>=</mo><mn>321</mn></mrow></math> Josephson junctions. It is shown that the Cherenkov wake behind the vortex shuttle trapped in the stack can trigger proliferation of counterpropagating vortices and antivortices which get synchronized and form large-amplitude standing electromagnetic waves. This happens if the dc current density <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>J</mi></math> exceeds a threshold value <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>J</mi><mi>s</mi></msub></math> which can be well below the Josephson interlayer critical current density <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>J</mi><mi>c</mi></msub></math> for underdamped junctions. The cavity modes stimulated by the vortex-antivortex pair production cause peaks in the radiated power <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>P</mi><mi>N</mi></msub><mrow><mo>(</mo><mi>J</mi><mo>)</mo></mrow></mrow></math> with a nearly monochromatic spectrum at discrete values of <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>J</mi></math> corresponding to the zero-field Fiske resonances. The power <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>P</mi><mi>N</mi></msub><mrow><mo>(</mo><mi>J</mi><mo>)</mo></mrow></mrow></math> was evaluated for small rectangular stacks in the magnetodipole approximation and for large stacks in a single mode state. For small stacks, the highest peak in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>P</mi><mi>N</mi></msub><mrow><mo>(</mo><mi>J</mi><mo>)</mo></mrow></mrow></math> increases rapidly, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>P</mi><mi>N</mi></msub><mo>∝</mo><msup><mi>N</mi><mn>6</mn></msup></mrow></math>, with the number of junctions at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>N</mi><mo>≤</mo><mn>81</mn></mrow></math> and gradually slows down to <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>P</mi><mi>N</mi></msub><mo>∝</mo><msup><mi>N</mi><mn>2</mn></msup></mrow></math> at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mn>161</mn><mo>≤</mo><mi>N</mi><mo>≤</mo><mn>321</mn></mrow></math>. For stacks larger than the radiation wavelength, we obtained <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>P</mi><mi>N</mi></msub><mo>∝</mo><msup><mi>N</mi><mn>5</mn></msup></mrow></math> at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>N</mi><mo>≲</mo><mn>200</mn><mo>–</mo><mn>300</mn></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>P</mi><mi>N</mi></msub><mo>∝</mo><msup><mi>N</mi><mn>2</mn></msup></mrow></math> at larger <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi></m
{"title":"Superradiant emission stimulated by vortex-antivortex pair production in layered superconductors","authors":"Alex Gurevich, Ahmad Sheikhzada","doi":"10.1103/physrevb.110.094501","DOIUrl":"https://doi.org/10.1103/physrevb.110.094501","url":null,"abstract":"We report numerical simulations of coupled sine-Gordon and heat diffusion equations describing dynamic states stimulated by a trapped vortex driven by dc current in a stack of up to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>N</mi><mo>=</mo><mn>321</mn></mrow></math> Josephson junctions. It is shown that the Cherenkov wake behind the vortex shuttle trapped in the stack can trigger proliferation of counterpropagating vortices and antivortices which get synchronized and form large-amplitude standing electromagnetic waves. This happens if the dc current density <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>J</mi></math> exceeds a threshold value <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>J</mi><mi>s</mi></msub></math> which can be well below the Josephson interlayer critical current density <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>J</mi><mi>c</mi></msub></math> for underdamped junctions. The cavity modes stimulated by the vortex-antivortex pair production cause peaks in the radiated power <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>P</mi><mi>N</mi></msub><mrow><mo>(</mo><mi>J</mi><mo>)</mo></mrow></mrow></math> with a nearly monochromatic spectrum at discrete values of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>J</mi></math> corresponding to the zero-field Fiske resonances. The power <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>P</mi><mi>N</mi></msub><mrow><mo>(</mo><mi>J</mi><mo>)</mo></mrow></mrow></math> was evaluated for small rectangular stacks in the magnetodipole approximation and for large stacks in a single mode state. For small stacks, the highest peak in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>P</mi><mi>N</mi></msub><mrow><mo>(</mo><mi>J</mi><mo>)</mo></mrow></mrow></math> increases rapidly, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>P</mi><mi>N</mi></msub><mo>∝</mo><msup><mi>N</mi><mn>6</mn></msup></mrow></math>, with the number of junctions at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>N</mi><mo>≤</mo><mn>81</mn></mrow></math> and gradually slows down to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>P</mi><mi>N</mi></msub><mo>∝</mo><msup><mi>N</mi><mn>2</mn></msup></mrow></math> at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>161</mn><mo>≤</mo><mi>N</mi><mo>≤</mo><mn>321</mn></mrow></math>. For stacks larger than the radiation wavelength, we obtained <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>P</mi><mi>N</mi></msub><mo>∝</mo><msup><mi>N</mi><mn>5</mn></msup></mrow></math> at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>N</mi><mo>≲</mo><mn>200</mn><mo>–</mo><mn>300</mn></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>P</mi><mi>N</mi></msub><mo>∝</mo><msup><mi>N</mi><mn>2</mn></msup></mrow></math> at larger <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>N</mi></m","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.094201
Daniel Gnida
The mystery of the field-independent behavior of resistivity in single-crystal is unraveled through the lens of interacting electrons in disordered systems. Consistent with theoretical predictions, our magnetotransport studies illuminate a scenario where a robust spin-orbit interaction renders the triplet term in the diffusion contribution ineffective. As a consequence, the magnetic field exerts no influence on the diffusion correction, giving sole dominance to weak localization and classical effects in shaping the magnetoresistance. In addition, marginal temperature variation of the weak localization at low temperatures results in the relation being predominantly dictated by the singlet term in the diffusion correction.
{"title":"Ineffectiveness of the triplet diffusion correction in the electron transport of disordered systems","authors":"Daniel Gnida","doi":"10.1103/physrevb.110.094201","DOIUrl":"https://doi.org/10.1103/physrevb.110.094201","url":null,"abstract":"The mystery of the field-independent <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mi>T</mi><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></math> behavior of resistivity in single-crystal <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Th</mi><mn>2</mn></msub><msub><mi>CoSi</mi><mn>3</mn></msub></mrow></math> is unraveled through the lens of interacting electrons in disordered systems. Consistent with theoretical predictions, our magnetotransport studies illuminate a scenario where a robust spin-orbit interaction renders the triplet term in the diffusion contribution ineffective. As a consequence, the magnetic field exerts no influence on the diffusion correction, giving sole dominance to weak localization and classical effects in shaping the magnetoresistance. In addition, marginal temperature variation of the weak localization at low temperatures results in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mi>T</mi><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></math> relation being predominantly dictated by the singlet term in the diffusion correction.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.104402
Manas Ranjan Mahapatra, Rakesh Kumar
Finding an exact solution for a realistic interacting quantum many-body problem is often challenging. There are only a few problems where an exact solution can be found, usually in a narrow parameter space. Here, we propose a spin- Heisenberg model on a square lattice with spatial anisotropy and bond depletion for the nearest-neighbor antiferromagnetic interactions but not for the next-nearest-neighbor interactions. This model has an exact and unique dimer ground state at ; a dimer state is a product state of spin singlets on dimers (here, staggered nearest-neighbor bonds). We examine this model by employing the bond-operator mean-field theory and exact diagonalization. These analytical and numerical methods precisely affirm the correctness of the dimer ground state at the exact point . As one moves away from the exact point, the dimer order melts and vanishes when the spin gap becomes zero. The mean-field theory with harmonic approximation indicates that the dimer order persists for . However, in nonharmonic approximation, the upper critical point lowers by 0.28 to 1.07, but the lower critical point remains intact. The exact diagonalization results suggest that the latter approximation fares better. The model reveals Néel order below the lower critical point and stripe magnetic order above the upper critical point. It has a topologically equivalent model on a honeycomb lattice where the nearest-neighbor interactions are still spatial anisotropic, but the bond depletion shifts into the isotropic next-neighbor interactions. Moreover, these models can also be generalized in the three dimensions.
{"title":"Exact staggered dimer ground state and its stability in a two-dimensional magnet","authors":"Manas Ranjan Mahapatra, Rakesh Kumar","doi":"10.1103/physrevb.110.104402","DOIUrl":"https://doi.org/10.1103/physrevb.110.104402","url":null,"abstract":"Finding an exact solution for a realistic interacting quantum many-body problem is often challenging. There are only a few problems where an exact solution can be found, usually in a narrow parameter space. Here, we propose a spin-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mfrac><mn>1</mn><mn>2</mn></mfrac></math> Heisenberg model on a square lattice with spatial anisotropy and bond depletion for the nearest-neighbor antiferromagnetic interactions but not for the next-nearest-neighbor interactions. This model has an <i>exact</i> and <i>unique</i> dimer ground state at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>J</mi><mn>2</mn></msub><mo>/</mo><msub><mi>J</mi><mn>1</mn></msub><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac></mrow></math>; a dimer state is a product state of spin singlets on dimers (here, staggered nearest-neighbor bonds). We examine this model by employing the bond-operator mean-field theory and exact diagonalization. These analytical and numerical methods precisely affirm the correctness of the dimer ground state at the exact point <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>(</mo><msub><mi>J</mi><mn>2</mn></msub><mo>/</mo><msub><mi>J</mi><mn>1</mn></msub><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mo>)</mo></mrow></math>. As one moves away from the exact point, the dimer order melts and vanishes when the spin gap becomes zero. The mean-field theory with harmonic approximation indicates that the dimer order persists for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>−</mo><mn>0.35</mn><mo>≲</mo><msub><mi>J</mi><mn>2</mn></msub><mo>/</mo><msub><mi>J</mi><mn>1</mn></msub><mo>≲</mo><mn>1.35</mn></mrow></math>. However, in nonharmonic approximation, the upper critical point lowers by 0.28 to 1.07, but the lower critical point remains intact. The exact diagonalization results suggest that the latter approximation fares better. The model reveals Néel order below the lower critical point and stripe magnetic order above the upper critical point. It has a topologically equivalent model on a honeycomb lattice where the nearest-neighbor interactions are still spatial anisotropic, but the bond depletion shifts into the isotropic next-neighbor interactions. Moreover, these models can also be generalized in the three dimensions.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report precise measurements to obtain the normal-state resistivity and the depairing current density of nanobridges along the axis, by using focused ion beam (FIB) techniques. We obtained both of the -plane and -axis resistivity and in the same part of a specimen, by fabricating the -axis nanobridge in the middle of a narrow bridge extended in the plane, in spite of the slight deficiency of P dopant due to the additional FIB fabrication. The normal-state resistivity anisotropy agreed with the previous results for bulk samples, showing just above the superconducting transition temperature, , in the slightly underdoped region and a slight decrease with increasing temperatures. The critical current density obtained in the -axis nanobridges near the optimal doping reaches at , corresponding to about 87% of a depairing limit derived by the Eilenberger equations. An extrapolation to K using the Ginzburg-Landau model suggests that the anisotropy of the depairing current density roughly corresponds to that of the normal-state resistivity. At low temperatures, we also observed a steplike voltage jump before arriving at the depairing limit, suggesting the occurrence of phase-slip phenomena near the depairing processes.
我们报告了利用聚焦离子束（FIB）技术获得 BaFe2(As1-xPx)2(x∼0.29-0.32)纳米电桥沿 c 轴的正态电阻率和去airing 电流密度的精确测量结果。尽管由于额外的 FIB 制作导致 P 掺杂剂略有不足，但通过在 ab 平面延伸的窄桥中间制作 c 轴纳米桥，我们在试样的同一部位获得了 ab 平面和 c 轴的电阻率（ρab 和 ρc）。正态电阻率各向异性与之前对块状样品的研究结果一致，在轻微掺杂不足的区域，ρc/ρab<8 恰好高于超导转变温度 Tc，并随着温度的升高而略有下降。在最佳掺杂附近的 c 轴纳米电桥中获得的临界电流密度在 0.15Tc 时达到 ∼8 MA/cm2，相当于艾伦伯格方程推导出的去airing 极限的 87%。利用金兹堡-朗道模型对 T=0 K 的推断表明，除气电流密度的各向异性大致与正常状态电阻率的各向异性一致。在低温条件下，我们还观察到在达到除气极限之前出现了阶跃式电压跳变，这表明在除气过程附近出现了相位滑移现象。
{"title":"Normal-state resistivity and the depairing current density of BaFe2(As,P)2 nanobridges along the c axis","authors":"Yuki Mizukoshi, Kotaro Jimbo, Akiyoshi Park, Yue Sun, Tsuyoshi Tamegai, Haruhisa Kitano","doi":"10.1103/physrevb.110.104501","DOIUrl":"https://doi.org/10.1103/physrevb.110.104501","url":null,"abstract":"We report precise measurements to obtain the normal-state resistivity and the depairing current density of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>BaFe</mi><mn>2</mn></msub><msub><mrow><mo>(</mo><msub><mi>As</mi><mrow><mn>1</mn><mo>−</mo><mi>x</mi></mrow></msub><msub><mi mathvariant=\"normal\">P</mi><mi>x</mi></msub><mo>)</mo></mrow><mn>2</mn></msub><mrow><mo>(</mo><mi>x</mi><mo>∼</mo><mn>0.29</mn><mo>−</mo><mn>0.32</mn><mo>)</mo></mrow></mrow></math> nanobridges along the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>c</mi></math> axis, by using focused ion beam (FIB) techniques. We obtained both of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>a</mi><mi>b</mi></mrow></math>-plane and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>c</mi></math>-axis resistivity <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>(</mo><msub><mi>ρ</mi><mrow><mi>a</mi><mi>b</mi></mrow></msub></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>ρ</mi><mi>c</mi></msub><mo>)</mo></math> in the same part of a specimen, by fabricating the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>c</mi></math>-axis nanobridge in the middle of a narrow bridge extended in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>a</mi><mi>b</mi></mrow></math> plane, in spite of the slight deficiency of P dopant due to the additional FIB fabrication. The normal-state resistivity anisotropy agreed with the previous results for bulk samples, showing <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>ρ</mi><mi>c</mi></msub><mo>/</mo><msub><mi>ρ</mi><mrow><mi>a</mi><mi>b</mi></mrow></msub><mo><</mo><mn>8</mn></mrow></math> just above the superconducting transition temperature, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi>c</mi></msub></math>, in the slightly underdoped region and a slight decrease with increasing temperatures. The critical current density obtained in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>c</mi></math>-axis nanobridges near the optimal doping reaches <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>∼</mo><mn>8</mn></mrow></math> <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>MA</mi><mo>/</mo><msup><mrow><mi>cm</mi></mrow><mn>2</mn></msup></math> at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>0.15</mn><msub><mi>T</mi><mi>c</mi></msub></mrow></math>, corresponding to about 87% of a depairing limit derived by the Eilenberger equations. An extrapolation to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>T</mi><mo>=</mo><mn>0</mn></mrow></math> K using the Ginzburg-Landau model suggests that the anisotropy of the depairing current density roughly corresponds to that of the normal-state resistivity. At low temperatures, we also observed a steplike voltage jump before arriving at the depairing limit, suggesting the occurrence of phase-slip phenomena near the depairing processes.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.104503
Jiong Mei, Kun Jiang, Shengshan Qin, Jiangping Hu
Intrinsic Rashba spin-orbital coupling (SOC) can exist in centrosymmetric materials with local inversion symmetry breaking. Here we show that such a SOC can induce topological superconductivity together with an in-plane Zeeman field in planar Josephson junctions formed by the centrosymmetric materials. A single Majorana mode can be created at each end of the junction. We demonstrate this result in a model respecting the same symmetry group with the iron-based superconductors. We derive the necessary Fermi surface condition for the topological planar junction and calculate the topological phase diagram with respect to the in-plane Zeeman field and the phase difference between the two superconductors. We provide experimental characteristics for the topological superconductivity, including the differential conductance and the Fano factor tomography which can be measured in the scanning tunneling spectroscopy. Our study reveals that the centrosymmetric systems with local-inversion-symmetry breaking can serve as new platforms for the topological planar Josephson junctions and helps to find more experimentally feasible materials for the topological superconductors.
{"title":"Inversion-symmetric electron gases as platforms for topological planar Josephson junctions","authors":"Jiong Mei, Kun Jiang, Shengshan Qin, Jiangping Hu","doi":"10.1103/physrevb.110.104503","DOIUrl":"https://doi.org/10.1103/physrevb.110.104503","url":null,"abstract":"Intrinsic Rashba spin-orbital coupling (SOC) can exist in centrosymmetric materials with local inversion symmetry breaking. Here we show that such a SOC can induce topological superconductivity together with an in-plane Zeeman field in planar Josephson junctions formed by the centrosymmetric materials. A single Majorana mode can be created at each end of the junction. We demonstrate this result in a model respecting the same symmetry group with the iron-based superconductors. We derive the necessary Fermi surface condition for the topological planar junction and calculate the topological phase diagram with respect to the in-plane Zeeman field and the phase difference between the two superconductors. We provide experimental characteristics for the topological superconductivity, including the differential conductance and the Fano factor tomography which can be measured in the scanning tunneling spectroscopy. Our study reveals that the centrosymmetric systems with local-inversion-symmetry breaking can serve as new platforms for the topological planar Josephson junctions and helps to find more experimentally feasible materials for the topological superconductors.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.l100301
Rohit Sharma, Martin Valldor, Thomas Lorenz
We report an investigation of the phonon thermal Hall effect in single crystal samples of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Y</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>Dy</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>DyYTi</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math>. We measured the field-linear thermal Hall effect in all three samples. The temperature dependence of thermal Hall conductivities shows a peak around 15 K, which coincides with the peak positions of the longitudinal thermal conductivities. The temperature-dependent longitudinal thermal conductivities indicates that phonons dominate thermal transport in all three samples. However, the presence of <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mrow><mi>Dy</mi></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math> magnetic ions introduces significant effects on the field dependence of the longitudinal thermal conductivities. The thermal Hall ratio is sizable in all three samples and consistent with the values reported for other insulating materials exhibiting a phononic thermal Hall effect, though their exact underlying mechanism remains yet to be identified. The thermal Hall ratio is nearly the same for <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Y</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>DyYTi</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math>, and slightly larger for <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>Dy</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math>, suggesting that magnetic impurities are less significant in generating the phononic thermal Hall effect. Our observations of the phononic thermal Hall effect support an intrinsic origin in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Y</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math> and suggest a combination of intrinsic and extrinsic effects in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>Dy</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>DyYTi</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>7</mn></msub></mrow></math
{"title":"Phonon thermal Hall effect in nonmagnetic Y2Ti2O7","authors":"Rohit Sharma, Martin Valldor, Thomas Lorenz","doi":"10.1103/physrevb.110.l100301","DOIUrl":"https://doi.org/10.1103/physrevb.110.l100301","url":null,"abstract":"We report an investigation of the phonon thermal Hall effect in single crystal samples of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Y</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>7</mn></msub></mrow></math>, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Dy</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>7</mn></msub></mrow></math>, and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>DyYTi</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>7</mn></msub></mrow></math>. We measured the field-linear thermal Hall effect in all three samples. The temperature dependence of thermal Hall conductivities shows a peak around 15 K, which coincides with the peak positions of the longitudinal thermal conductivities. The temperature-dependent longitudinal thermal conductivities indicates that phonons dominate thermal transport in all three samples. However, the presence of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>Dy</mi></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math> magnetic ions introduces significant effects on the field dependence of the longitudinal thermal conductivities. The thermal Hall ratio is sizable in all three samples and consistent with the values reported for other insulating materials exhibiting a phononic thermal Hall effect, though their exact underlying mechanism remains yet to be identified. The thermal Hall ratio is nearly the same for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Y</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>7</mn></msub></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>DyYTi</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>7</mn></msub></mrow></math>, and slightly larger for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Dy</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>7</mn></msub></mrow></math>, suggesting that magnetic impurities are less significant in generating the phononic thermal Hall effect. Our observations of the phononic thermal Hall effect support an intrinsic origin in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Y</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>7</mn></msub></mrow></math> and suggest a combination of intrinsic and extrinsic effects in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Dy</mi><mn>2</mn></msub><msub><mi>Ti</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>7</mn></msub></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>DyYTi</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>7</mn></msub></mrow></math","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.094306
Francesco Macheda, Paolo Barone, Francesco Mauri
Within the context of first-principles techniques, we present a theoretical and computational framework to quickly determine, at finite momentum, the static self-consistent (longitudinal) charge response to an external perturbation that enters the determination of the scattering cross section of inelastic scattering processes such as EELS. We also determine the (transverse) charge response computed in short-circuit conditions. The all-order quasimomentum expansion of the transverse charge response to an atomic displacement are identified with dynamical Born effective charges, quadrupoles, octupoles, etc. Theoretically, we demonstrate that the transverse charge response can be related to the longitudinal one via a well-defined static long-range dielectric function, going beyond the random phase approximation. Our theoretical advancements allow for an efficient use of perturbation theory in the computational implementation. Due to its more favorable scaling, our method provides an interesting alternative to the use of the theorem, especially for the study of semiconductors and metals with large unit cells. For semiconductors, we apply our developments to the computation of the piezoelectric properties of a large cell solid solution of semiconducting hafnium oxide containing 96 atoms. We here show that the clamped ion piezoelectric response, which is determined solely by dynamical quadrupoles, can be decomposed into real-space localized contributions that mostly depend on the chemical environment, paving the way for the use of machine-learning techniques in the material search for optimized piezoelectrics. We further apply our methodology to determine the density response of metals. We here find that the leading terms of the charge expansion are related to the Fermi energy shift of the potential if admitted by symmetry, and by Born effective charges which do not sum to zero over the atoms. These terms are then linked to the leading order expansion of the macroscopic electron-phonon coupling in metals. We apply our developments to the TEM-EELS spectroscopy of lithium intercalated graphites, where we find that approximating the density response via the use of the atomic form-factor in the long-wavelength limit does not take into account the anisotropy of the atomic chemical bonding in the crystal.
{"title":"First-principles calculations of dynamical Born effective charges, quadrupoles, and higher order terms from the charge response in large semiconducting and metallic systems","authors":"Francesco Macheda, Paolo Barone, Francesco Mauri","doi":"10.1103/physrevb.110.094306","DOIUrl":"https://doi.org/10.1103/physrevb.110.094306","url":null,"abstract":"Within the context of first-principles techniques, we present a theoretical and computational framework to quickly determine, at finite momentum, the static self-consistent (longitudinal) charge response to an external perturbation that enters the determination of the scattering cross section of inelastic scattering processes such as EELS. We also determine the (transverse) charge response computed in short-circuit conditions. The all-order quasimomentum expansion of the transverse charge response to an atomic displacement are identified with dynamical Born effective charges, quadrupoles, octupoles, etc. Theoretically, we demonstrate that the transverse charge response can be related to the longitudinal one via a well-defined static long-range dielectric function, going beyond the random phase approximation. Our theoretical advancements allow for an efficient use of perturbation theory in the computational implementation. Due to its more favorable scaling, our method provides an interesting alternative to the use of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>2</mn><mi>n</mi><mo>+</mo><mn>1</mn></mrow></math> theorem, especially for the study of semiconductors and metals with large unit cells. For semiconductors, we apply our developments to the computation of the piezoelectric properties of a large cell solid solution of semiconducting hafnium oxide containing 96 atoms. We here show that the clamped ion piezoelectric response, which is determined solely by dynamical quadrupoles, can be decomposed into real-space localized contributions that mostly depend on the chemical environment, paving the way for the use of machine-learning techniques in the material search for optimized piezoelectrics. We further apply our methodology to determine the density response of metals. We here find that the leading terms of the charge expansion are related to the Fermi energy shift of the potential if admitted by symmetry, and by Born effective charges which do not sum to zero over the atoms. These terms are then linked to the leading order expansion of the macroscopic electron-phonon coupling in metals. We apply our developments to the TEM-EELS spectroscopy of lithium intercalated graphites, where we find that approximating the density response via the use of the atomic form-factor in the long-wavelength limit does not take into account the anisotropy of the atomic chemical bonding in the crystal.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.094404
Yuto Ashida, Shunsuke Furukawa, Masaki Oshikawa
Entanglement in quantum many-body systems can exhibit universal phenomena governed by long-distance properties. We study universality and phase transitions of the entanglement inherent to open many-body systems, namely, the entanglement between a system of interest and its environment. Specifically, we consider the Tomonaga-Luttinger liquid (TLL) under a local measurement and analyze its unconditioned nonunitary evolution, where the measurement outcomes are averaged over. We quantify the system-environment entanglement by the Rényi entropy of the post-measurement density matrix, whose size-independent term encodes the universal low-energy physics. We develop a field-theoretical description to relate the universal term to the effective ground-state degeneracy known as the function in a boundary conformal field theory, and use the renormalization group method to determine its value. We show that the universal contribution is determined by the TLL parameter and can exhibit singularity signifying an entanglement phase transition. Surprisingly, in certain cases the size-independent contribution can increase as a function of the measurement strength in contrast to what is naïvely expected from the -theorem. We argue that this unconventional behavior could be attributed to the dangerously irrelevant term which has been found in studies of the resistively shunted Josephson junction. We also check these results by numerical calculations in the spin- XXZ chain subject to a site-resolved measurement. Possible experimental realization in ultracold gases, which requires no postselections, is discussed.
量子多体系统中的纠缠可以表现出受长距离特性支配的普遍现象。我们研究开放多体系统固有纠缠的普遍性和相变，即相关系统与其环境之间的纠缠。具体来说，我们考虑了局部测量下的 Tomonaga-Luttinger 液体 (TLL)，并分析了其无条件非单元演化，其中测量结果被平均化。我们通过测量后密度矩阵的雷尼熵来量化系统与环境之间的纠缠，其大小无关项编码了普遍的低能物理。我们发展了一种场论描述，将普遍项与边界共形场论中被称为 g 函数的有效基态退化联系起来，并使用重正化群方法确定其值。我们的研究表明，普适贡献由 TLL 参数 K 决定，并可能表现出标志着纠缠相变的奇异性。令人惊讶的是，在某些情况下，与尺寸无关的贡献会随着测量强度的增加而增加，这与 g 定理的天真预期截然不同。我们认为，这种非常规行为可归因于在研究电阻分流约瑟夫森结时发现的危险无关项。我们还通过自旋-12 XXZ 链的数值计算检验了这些结果，并进行了定点分辨测量。我们还讨论了在超冷气体中实现无需后选择的实验可能性。
{"title":"System-environment entanglement phase transitions","authors":"Yuto Ashida, Shunsuke Furukawa, Masaki Oshikawa","doi":"10.1103/physrevb.110.094404","DOIUrl":"https://doi.org/10.1103/physrevb.110.094404","url":null,"abstract":"Entanglement in quantum many-body systems can exhibit universal phenomena governed by long-distance properties. We study universality and phase transitions of the entanglement inherent to open many-body systems, namely, the entanglement between a system of interest and its environment. Specifically, we consider the Tomonaga-Luttinger liquid (TLL) under a local measurement and analyze its unconditioned nonunitary evolution, where the measurement outcomes are averaged over. We quantify the system-environment entanglement by the Rényi entropy of the post-measurement density matrix, whose size-independent term encodes the universal low-energy physics. We develop a field-theoretical description to relate the universal term to the effective ground-state degeneracy known as the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>g</mi></math> function in a boundary conformal field theory, and use the renormalization group method to determine its value. We show that the universal contribution is determined by the TLL parameter <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>K</mi></math> and can exhibit singularity signifying an entanglement phase transition. Surprisingly, in certain cases the size-independent contribution can increase as a function of the measurement strength in contrast to what is naïvely expected from the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>g</mi></math>-theorem. We argue that this unconventional behavior could be attributed to the dangerously irrelevant term which has been found in studies of the resistively shunted Josephson junction. We also check these results by numerical calculations in the spin-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mfrac><mn>1</mn><mn>2</mn></mfrac></math> XXZ chain subject to a site-resolved measurement. Possible experimental realization in ultracold gases, which requires no postselections, is discussed.","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1103/physrevb.110.104401
Deepak Garg, Amit Kumar, S. M. Yusuf
In this paper, we present a comprehensive investigation of the distinctive magnetic properties involving the remarkable occurrences of negative magnetization (NM), exchange bias (EB), and spin reorientation (SR) in the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>ErF</mi><msub><mi mathvariant="normal">e</mi><mrow><mn>0.5</mn></mrow></msub><msub><mi mathvariant="normal">Co</mi><mrow><mn>0.5</mn></mrow></msub><msub><mi mathvariant="normal">O</mi><mn>3</mn></msub></mrow></math> compound. The dc magnetization data, recorded in field-cooled-cooling mode, reveal a net zero magnetization at the compensation temperature <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>(</mo><msub><mi>T</mi><mi>COMP</mi></msub><mo>)</mo></math> of 24 K, leading to the NM phenomenon in the compound. Rietveld refinement of the neutron diffraction (ND) patterns over 1.5–300 K elucidates the SR of Fe/Co spins at 100 K <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>(</mo><msub><mi>T</mi><mi>SR</mi></msub><mo>)</mo></math> and Er magnetic ordering <4 K <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>(</mo><msubsup><mi>T</mi><mrow><mi mathvariant="normal">N</mi></mrow><mi>Er</mi></msubsup><mo>)</mo></math> resulting in <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi mathvariant="normal">Γ</mi><mn>4</mn></msub><mo>(</mo><msub><mi>G</mi><mi>x</mi></msub><mo>)</mo></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi mathvariant="normal">Γ</mi><mn>24</mn></msub><mo>(</mo><mrow><msub><mi>G</mi><mi>z</mi></msub><mo>,</mo><msub><mi>G</mi><mi>x</mi></msub><mo>)</mo></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi mathvariant="normal">Γ</mi><mn>2</mn></msub><mo>(</mo><msub><mi>G</mi><mi>z</mi></msub><mo>)</mo></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi mathvariant="normal">Γ</mi><mn>257</mn></msub><mo>(</mo><mrow><msub><mi>G</mi><mi>z</mi></msub><mo>;</mo><msubsup><mi>A</mi><mi>y</mi><mi>Er</mi></msubsup><msubsup><mi>G</mi><mi>z</mi><mi>Er</mi></msubsup><mo>)</mo></mrow></math> magnetic structures at <i>T</i> > <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>T</mi><mi>SR</mi></msub></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>T</mi><mi>SR</mi></msub><mo>≥</mo><mi>T</mi><mo>></mo><msub><mi>T</mi><mi>COMP</mi></msub></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msubsup><mi>T</mi><mrow><mi mathvariant="normal">N</mi></mrow><mi>Er</mi></msubsup><mo><</mo><mi>T</mi><mo>≤</mo><msub><mi>T</mi><mi>COMP</mi></msub></mrow></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>T</mi><mspace width="0.16em"></mspace><mo>≤</mo><mspace width="0.16em"></mspace><msubsup><mi>T</mi><mrow><mi mathvariant="normal">N</mi></mrow><mi>Er</mi></msubsup></mrow></math>, respectively. It is, therefore, evident that the SR of Fe/Co moments from <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi mathvariant="n
本文全面研究了 ErFe0.5Co0.5O3 复合物中显著出现的负磁化（NM）、交换偏置（EB）和自旋重新定向（SR）等独特磁性能。以场冷却-冷却模式记录的直流磁化数据显示，在 24 K 的补偿温度 (TCOMP) 下磁化率为零，从而导致了化合物中的负磁化现象。在 1.5-300 K 的中子衍射 (ND) 图样进行了里特维尔德细化，阐明了在 100 K (TSR) 和 Er 磁有序 <4 K (TNEr) 下铁/钴自旋的 SR，分别在 T >TSR、TSR≥T>TCOMP、TNEr<T≤TCOMP 和 T≤TNEr 时产生Γ4(Gx)、Γ24(Gz,Gx)、Γ2(Gz) 和Γ257(Gz;AyErGzEr) 磁结构。因此很明显，铁/钴矩从Γ4（Gx）到Γ2（Gz）的 SR 是在 24 K 的 TCOMP 时完成的，而 Er 磁有序变成不寻常的Γ57（AyErGzEr）自旋构型是在 T≤4 K 时发生的。有趣的是，化合物中的 EB 场（HEB）在整个 TCOMP 期间极性不变，甚至在 TCOMP 以上仍为正值。从 ND 可以看出，在 T > TCOMP 时观察到的正 HEB 可归因于复杂的自旋排列，而在 T ≤ TCOMP 时，正 HEB 通常可在 Meiklejohn-Beam 模型框架内得到解释。在 TCOMP 和 TSR 时，正 HEB 的最大值和 HEB 的宽驼峰分别表明了化合物中 EB 和 SR 之间的相关性。此外，EB 与冷却场的关系显示出一个峰值，即 5 kOe；此后，发现 HEB 在冷却场达到 70 kOe 时受到异常抑制。利用库克模型（Cooke's model）阐明了在 TCOMP 以下观察到的 NM，在该模型中，极化的 Er 磁矩在有序悬臂反铁磁性铁/钴亚晶格的内部磁场作用下，与铁磁性铁/钴磁矩竞争。这导致化合物在 TCOMP 时磁化完全消失，而在 TCOMP 以下出现 NM。比热数据显示了肖特基反常现象，从而推断出铒矩在 TCOMP 以下的主要极化性质。在本文中，我们强调了 Er 和铁/钴交换耦合在形成该化合物奇妙而复杂的磁性能（NM 和 EB）中的关键作用。这些发现凸显了该化合物在自旋电子应用中的潜在用途。
{"title":"Unraveling intricate magnetic behavior involving negative magnetization and exchange-bias in ErFe0.5Co0.5O3","authors":"Deepak Garg, Amit Kumar, S. M. Yusuf","doi":"10.1103/physrevb.110.104401","DOIUrl":"https://doi.org/10.1103/physrevb.110.104401","url":null,"abstract":"In this paper, we present a comprehensive investigation of the distinctive magnetic properties involving the remarkable occurrences of negative magnetization (NM), exchange bias (EB), and spin reorientation (SR) in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>ErF</mi><msub><mi mathvariant=\"normal\">e</mi><mrow><mn>0.5</mn></mrow></msub><msub><mi mathvariant=\"normal\">Co</mi><mrow><mn>0.5</mn></mrow></msub><msub><mi mathvariant=\"normal\">O</mi><mn>3</mn></msub></mrow></math> compound. The dc magnetization data, recorded in field-cooled-cooling mode, reveal a net zero magnetization at the compensation temperature <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>(</mo><msub><mi>T</mi><mi>COMP</mi></msub><mo>)</mo></math> of 24 K, leading to the NM phenomenon in the compound. Rietveld refinement of the neutron diffraction (ND) patterns over 1.5–300 K elucidates the SR of Fe/Co spins at 100 K <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>(</mo><msub><mi>T</mi><mi>SR</mi></msub><mo>)</mo></math> and Er magnetic ordering <4 K <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>(</mo><msubsup><mi>T</mi><mrow><mi mathvariant=\"normal\">N</mi></mrow><mi>Er</mi></msubsup><mo>)</mo></math> resulting in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">Γ</mi><mn>4</mn></msub><mo>(</mo><msub><mi>G</mi><mi>x</mi></msub><mo>)</mo></math>, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">Γ</mi><mn>24</mn></msub><mo>(</mo><mrow><msub><mi>G</mi><mi>z</mi></msub><mo>,</mo><msub><mi>G</mi><mi>x</mi></msub><mo>)</mo></mrow></math>, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">Γ</mi><mn>2</mn></msub><mo>(</mo><msub><mi>G</mi><mi>z</mi></msub><mo>)</mo></math>, and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">Γ</mi><mn>257</mn></msub><mo>(</mo><mrow><msub><mi>G</mi><mi>z</mi></msub><mo>;</mo><msubsup><mi>A</mi><mi>y</mi><mi>Er</mi></msubsup><msubsup><mi>G</mi><mi>z</mi><mi>Er</mi></msubsup><mo>)</mo></mrow></math> magnetic structures at <i>T</i> > <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi>SR</mi></msub></math>, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>T</mi><mi>SR</mi></msub><mo>≥</mo><mi>T</mi><mo>></mo><msub><mi>T</mi><mi>COMP</mi></msub></mrow></math>, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msubsup><mi>T</mi><mrow><mi mathvariant=\"normal\">N</mi></mrow><mi>Er</mi></msubsup><mo><</mo><mi>T</mi><mo>≤</mo><msub><mi>T</mi><mi>COMP</mi></msub></mrow></math>, and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>T</mi><mspace width=\"0.16em\"></mspace><mo>≤</mo><mspace width=\"0.16em\"></mspace><msubsup><mi>T</mi><mrow><mi mathvariant=\"normal\">N</mi></mrow><mi>Er</mi></msubsup></mrow></math>, respectively. It is, therefore, evident that the SR of Fe/Co moments from <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"n","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142123561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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