Pub Date : 2024-09-10DOI: 10.1103/physrevmaterials.8.093603
Michael Widom
The AlCrTiV high entropy alloy undergoes an order-disorder transition from body-centered cubic (Strukturbericht A2) at high temperatures to the CsCl structure (B2) at intermediate temperatures. We model this transition using first principles Monte Carlo/molecular dynamics simulations. Simulation results yield the temperature-dependent energy, entropy, heat capacity, occupancy fluctuations, and diffraction patterns. The contribution of chemical disorder to the entropy is calculated on the basis of point and pair cluster frequencies. The simulated structures exhibit compensated ferrimagnetism, and the Fermi level lies in a pseudogap. Sensitivity of structure and magnetism to the exchange-correlation functional is discussed, and neutron diffraction experiments are proposed to help resolve the true chemical order.
{"title":"First-principles study of the order-disorder transition in the AlCrTiV high entropy alloy","authors":"Michael Widom","doi":"10.1103/physrevmaterials.8.093603","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093603","url":null,"abstract":"The AlCrTiV high entropy alloy undergoes an order-disorder transition from body-centered cubic (Strukturbericht A2) at high temperatures to the CsCl structure (B2) at intermediate temperatures. We model this transition using first principles Monte Carlo/molecular dynamics simulations. Simulation results yield the temperature-dependent energy, entropy, heat capacity, occupancy fluctuations, and diffraction patterns. The contribution of chemical disorder to the entropy is calculated on the basis of point and pair cluster frequencies. The simulated structures exhibit compensated ferrimagnetism, and the Fermi level lies in a pseudogap. Sensitivity of structure and magnetism to the exchange-correlation functional is discussed, and neutron diffraction experiments are proposed to help resolve the true chemical order.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"10 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1103/physrevmaterials.8.094001
A. Brassington, Q. Ma, G. Sala, A. I. Kolesnikov, K. M. Taddei, Y. Wu, E. S. Choi, H. Wang, W. Xie, J. Ma, H. D. Zhou, A. A. Aczel
Polycrystalline and single-crystal samples of the insulating Shastry-Sutherland compound were synthesized via a solid-state reaction and the floating zone method, respectively. The crystal structure, Er single-ion anisotropy, zero-field magnetic ground state, and magnetic phase diagrams along high-symmetry crystallographic directions were investigated with bulk measurement techniques, x-ray and neutron diffraction, and neutron spectroscopy. We establish that crystallizes in a tetragonal space group with planes of orthogonal Er dimers and a strong preference for the Er moments to lie in the local plane perpendicular to each dimer bond. We also find that this system has a noncollinear ordered ground state in zero field with a transition temperature of 0.841 K consisting of antiferromagnetic dimers and in-plane moments. Finally, we mapped out the phase diagrams for along the directions [001], [100], and [110]. While an increasing in-plane field simply induces a phase transition to a field-polarized phase, we identify three metamagnetic transitions in the [001] case. Single-crystal neutron diffraction results reveal that the [001] phase diagram can be explained predominantly by the expected field-induced behavior of classical, anisotropic moments, although the microscopic origin of one phase requires further investigation.
{"title":"Magnetic properties of the quasi-XY Shastry-Sutherland magnet Er2Be2SiO7","authors":"A. Brassington, Q. Ma, G. Sala, A. I. Kolesnikov, K. M. Taddei, Y. Wu, E. S. Choi, H. Wang, W. Xie, J. Ma, H. D. Zhou, A. A. Aczel","doi":"10.1103/physrevmaterials.8.094001","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094001","url":null,"abstract":"Polycrystalline and single-crystal samples of the insulating Shastry-Sutherland compound <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Er</mi><mn>2</mn></msub><msub><mi>Be</mi><mn>2</mn></msub><msub><mi>SiO</mi><mn>7</mn></msub></mrow></math> were synthesized via a solid-state reaction and the floating zone method, respectively. The crystal structure, Er single-ion anisotropy, zero-field magnetic ground state, and magnetic phase diagrams along high-symmetry crystallographic directions were investigated with bulk measurement techniques, x-ray and neutron diffraction, and neutron spectroscopy. We establish that <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Er</mi><mn>2</mn></msub><msub><mi>Be</mi><mn>2</mn></msub><msub><mi>SiO</mi><mn>7</mn></msub></mrow></math> crystallizes in a tetragonal space group with planes of orthogonal Er dimers and a strong preference for the Er moments to lie in the local plane perpendicular to each dimer bond. We also find that this system has a noncollinear ordered ground state in zero field with a transition temperature of 0.841 K consisting of antiferromagnetic dimers and in-plane moments. Finally, we mapped out the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi><mtext>−</mtext><mi>T</mi></mrow></math> phase diagrams for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Er</mi><mn>2</mn></msub><msub><mi>Be</mi><mn>2</mn></msub><msub><mi>SiO</mi><mn>7</mn></msub></mrow></math> along the directions <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi><mo>∥</mo></mrow></math> [001], [100], and [110]. While an increasing in-plane field simply induces a phase transition to a field-polarized phase, we identify three metamagnetic transitions in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi><mo>∥</mo></mrow></math> [001] case. Single-crystal neutron diffraction results reveal that the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi><mo>∥</mo></mrow></math> [001] phase diagram can be explained predominantly by the expected field-induced behavior of classical, anisotropic moments, although the microscopic origin of one phase requires further investigation.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"8 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1103/physrevmaterials.8.l091401
Anouk S. Goossens, Kartik Samanta, Azminul Jaman, Wissem Boubaker, Job J. L. van Rijn, Evgeny Y. Tsymbal, Tamalika Banerjee
Magnetic tunnel junctions (MTJs) that are comprised of epitaxially grown complex oxides offer a versatile platform to control the symmetry of tunneling states and tailor magnetic anisotropy useful for practical applications. This work employs thin films of as an insulating barrier deposited between two ferromagnetic electrodes to form fully epitaxial MTJs and demonstrate these functionalities. Transport measurements demonstrate large tunneling magnetoresistance (TMR), significantly exceeding previously found values of TMR in MTJs based on electrodes. These results are explained by perpendicular magnetic anisotropy of and matching (mismatching) between symmetry and spin across the (001) interface for the parallel (antiparallel) MTJ magnetization state, supported by density functional (DFT) calculations. The angular variation of TMR indicates that the electrodes contain multiple magnetic domains, allowing the devices to exhibit at least three stable resistance states.
{"title":"Symmetry-driven large tunneling magnetoresistance in SrRuO3 magnetic tunnel junctions with perpendicular magnetic anisotropy","authors":"Anouk S. Goossens, Kartik Samanta, Azminul Jaman, Wissem Boubaker, Job J. L. van Rijn, Evgeny Y. Tsymbal, Tamalika Banerjee","doi":"10.1103/physrevmaterials.8.l091401","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.l091401","url":null,"abstract":"Magnetic tunnel junctions (MTJs) that are comprised of epitaxially grown complex oxides offer a versatile platform to control the symmetry of tunneling states and tailor magnetic anisotropy useful for practical applications. This work employs thin films of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>SrTiO</mi><mn>3</mn></msub></math> as an insulating barrier deposited between two ferromagnetic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>SrRuO</mi><mn>3</mn></msub></math> electrodes to form fully epitaxial MTJs and demonstrate these functionalities. Transport measurements demonstrate large tunneling magnetoresistance (TMR), significantly exceeding previously found values of TMR in MTJs based on <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>SrRuO</mi><mn>3</mn></msub></math> electrodes. These results are explained by perpendicular magnetic anisotropy of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>SrRuO</mi><mn>3</mn></msub></math> and matching (mismatching) between symmetry and spin across the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>SrTiO</mi><mn>3</mn></msub><mo>/</mo><msub><mi>SrRuO</mi><mn>3</mn></msub></mrow></math> (001) interface for the parallel (antiparallel) MTJ magnetization state, supported by density functional (DFT) calculations. The angular variation of TMR indicates that the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>SrRuO</mi><mn>3</mn></msub></math> electrodes contain multiple magnetic domains, allowing the devices to exhibit at least three stable resistance states.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"110 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-09DOI: 10.1103/physrevmaterials.8.094801
Sijia Tu, Jinsong Zhang, Zefeng Lin, Beiyi Zhu, Qihong Chen, Jie Yuan, Kui Jin
We report a systematic study of the thickness effect on the superconductivity of overdoped films. As the film thickness decreases, a recurrence of superconductivity is observed in the film, while this doping level is commonly expected to show Fermi liquid behavior. The superconducting critical temperatures exhibit a domelike shape with varying thickness. The magnetic susceptibility measurements suggest that the presence of superconductivity in thin films should be filamentary. The combined effect of stress and oxygen in the thickness-gradient films is proposed to comprehend the experimental observations. Our findings provide new perspectives on superconductivity in other systems, such as the hotly debated nickelate superconductors.
{"title":"Recurrence of superconductivity in thickness-gradient La1.81Ce0.19CuO4−δ film","authors":"Sijia Tu, Jinsong Zhang, Zefeng Lin, Beiyi Zhu, Qihong Chen, Jie Yuan, Kui Jin","doi":"10.1103/physrevmaterials.8.094801","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094801","url":null,"abstract":"We report a systematic study of the thickness effect on the superconductivity of overdoped <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">L</mi><msub><mi mathvariant=\"normal\">a</mi><mrow><mn>2</mn><mo>−</mo><mi>x</mi></mrow></msub><mi mathvariant=\"normal\">C</mi><msub><mi mathvariant=\"normal\">e</mi><mi>x</mi></msub><mi>Cu</mi><msub><mi mathvariant=\"normal\">O</mi><mrow><mn>4</mn><mo>−</mo><mi>δ</mi></mrow></msub></mrow></math> films. As the film thickness decreases, a recurrence of superconductivity is observed in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>x</mi><mo>=</mo><mn>0.19</mn></mrow></math> film, while this doping level is commonly expected to show Fermi liquid behavior. The superconducting critical temperatures exhibit a domelike shape with varying thickness. The magnetic susceptibility measurements suggest that the presence of superconductivity in thin films should be filamentary. The combined effect of stress and oxygen in the thickness-gradient films is proposed to comprehend the experimental observations. Our findings provide new perspectives on superconductivity in other systems, such as the hotly debated nickelate superconductors.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"45 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report a layered transition-metal-ordered oxypnictide . The new material was synthesized by solid-state reactions under vacuum. It has an intergrowth structure with a perovskite-like unit and -type block stacking coherently along the crystallographic axis. The measurements of electrical resistivity, magnetic susceptibility, and specific heat indicate metallic conductivity from the CoAs layers and short-range antiferromagnetic ordering in the planes. No itinerant-electron ferromagnetism expected in CoAs layers is observed. This result, combined with the first-principles calculations and the previous reports of other CoAs-layer-based materials, suggests that the bond length plays a crucial role in the emergence of itinerant ferromagnetism.
我们报告了一种层状过渡金属有序氧化锑 Sr2CrCoAsO3。这种新材料是在真空条件下通过固态反应合成的。它具有一种互生结构，其中包晶型 Sr3Cr2O6 单元和 ThCr2Si2 型 SrCo2As2 嵌段沿晶体学 c 轴相干堆叠。电阻率、磁感应强度和比热的测量结果表明，CoAs 层具有金属导电性，CrO2 平面具有短程反铁磁有序性。在 CoAs 层中没有观察到预期的迭电子铁磁性。这一结果与第一原理计算结果以及之前关于其他 CoAs 层基材料的报道相结合，表明 Co-Co 键长度在巡回铁磁性的出现中起着至关重要的作用。
{"title":"Absence of itinerant ferromagnetism in a cobalt-based oxypnictide","authors":"Hua-Xun Li, Hao Jiang, Yi-Qiang Lin, Jia-Xin Li, Shi-Jie Song, Qin-Qing Zhu, Zhi Ren, Guang-Han Cao","doi":"10.1103/physrevmaterials.8.094405","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094405","url":null,"abstract":"We report a layered transition-metal-ordered oxypnictide <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Sr</mi><mn>2</mn></msub><msub><mi>CrCoAsO</mi><mn>3</mn></msub></mrow></math>. The new material was synthesized by solid-state reactions under vacuum. It has an intergrowth structure with a perovskite-like <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Sr</mi><mn>3</mn></msub><msub><mi>Cr</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>6</mn></msub></mrow></math> unit and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>ThCr</mi><mn>2</mn></msub><msub><mi>Si</mi><mn>2</mn></msub></mrow></math>-type <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>SrCo</mi><mn>2</mn></msub><msub><mi>As</mi><mn>2</mn></msub></mrow></math> block stacking coherently along the crystallographic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>c</mi></math> axis. The measurements of electrical resistivity, magnetic susceptibility, and specific heat indicate metallic conductivity from the CoAs layers and short-range antiferromagnetic ordering in the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>CrO</mi><mn>2</mn></msub></math> planes. No itinerant-electron ferromagnetism expected in CoAs layers is observed. This result, combined with the first-principles calculations and the previous reports of other CoAs-layer-based materials, suggests that the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Co</mi><mo>−</mo><mi>Co</mi></mrow></math> bond length plays a crucial role in the emergence of itinerant ferromagnetism.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The site-selective substitution of diamagnetic cations offers an efficient way to fine-tune magnetic characteristics by controlling orbital hybridization and superexchange pathways. Herein, we explore the tunability of magnetic properties in coupled spin-ladder compounds (). The pristine compound exhibits spin-singlet correlations at elevated temperatures, as evidenced by a magnetic susceptibility peak at K, Schottky-like specific heat, unconventional magnetic Raman scattering, and a quasilinear decrease in the electron spin resonance linewidth. Notably, the substitution of for brings about several marked changes: an increase in the Curie-Weiss temperature, a suppression in the Néel ordering temperature, enhanced magnetic susceptibility at low temperatures, and a weakening of spin-ladder correlations. These modifications collectively suggest that the newly activated exchange interactions through substitution primarily alter intraladder spin topology while amplifying quantum critical fluctuations. This finding highlights the potential for controlling magnetic correlations in spin-ladder compounds through targeted chemical substitution.
{"title":"Tuning magnetic correlations in s=1/2 spin ladder Ba2CuTe1−xWxO6 through site-selective cation substitution","authors":"Muskan Sande, Joydev Khatua, Youngsu Choi, Kwang-Yong Choi","doi":"10.1103/physrevmaterials.8.094404","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094404","url":null,"abstract":"The site-selective substitution of diamagnetic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mrow><mi>d</mi></mrow><mn>10</mn></msup><mo>/</mo><msup><mrow><mi>d</mi></mrow><mn>0</mn></msup></mrow></math> cations offers an efficient way to fine-tune magnetic characteristics by controlling orbital hybridization and superexchange pathways. Herein, we explore the tunability of magnetic properties in coupled spin-ladder compounds <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">B</mi><msub><mi mathvariant=\"normal\">a</mi><mn>2</mn></msub><mi>CuT</mi><msub><mi mathvariant=\"normal\">e</mi><mrow><mn>1</mn><mrow><mtext>−</mtext><mi>x</mi></mrow></mrow></msub><msub><mi mathvariant=\"normal\">W</mi><mi>x</mi></msub><msub><mi mathvariant=\"normal\">O</mi><mn>6</mn></msub></mrow></math> (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>x</mi><mo>=</mo><mn>0.0</mn><mo>−</mo><mn>0.30</mn></mrow></math>). The pristine compound exhibits spin-singlet correlations at elevated temperatures, as evidenced by a magnetic susceptibility peak at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>T</mi><mi>max</mi></msub><mo>∼</mo><mn>70</mn></mrow></math> K, Schottky-like specific heat, unconventional magnetic Raman scattering, and a quasilinear decrease in the electron spin resonance linewidth. Notably, the substitution of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi mathvariant=\"normal\">W</mi></mrow><mrow><mn>6</mn><mo>+</mo></mrow></msup></math> for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">T</mi><msup><mrow><mi mathvariant=\"normal\">e</mi></mrow><mrow><mn>6</mn><mo>+</mo></mrow></msup></mrow></math> brings about several marked changes: an increase in the Curie-Weiss temperature, a suppression in the Néel ordering temperature, enhanced magnetic susceptibility at low temperatures, and a weakening of spin-ladder correlations. These modifications collectively suggest that the newly activated exchange interactions through <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi mathvariant=\"normal\">W</mi></mrow><mrow><mn>6</mn><mo>+</mo></mrow></msup></math> substitution primarily alter intraladder spin topology while amplifying quantum critical fluctuations. This finding highlights the potential for controlling magnetic correlations in spin-ladder compounds through targeted chemical substitution.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"57 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-06DOI: 10.1103/physrevmaterials.8.095201
Qiaoling Chen, Qianshan Quan, Chang-Kui Duan
The poor understanding of the optical transitions and luminescent mechanisms critically hindered the development of near-infrared (NIR) -activated phosphors, and efficient luminescence from Fe(Oh) has rarely been reported. In our study, we delve into these challenges and realize their correlation with the quenching mechanism of luminescence. First-principles calculations are utilized to analyze energy levels and electron-phonon coupling parameters, further elucidating potential deactivation pathways and factors influencing the occurrence of photoluminescence. A heuristic rule based on ligand-field strength, determined by the absorption wavelength of occupying the same octahedral site in oxides, is proposed to facilitate the prediction of both the potential and wavelength of emission. Our study offers consistent and reliable interpretations for the difficulties and challenges of iron-doped crystals, and provides valuable insights on the design and optimization of -based phosphors.
{"title":"Uncovering the presence or absence of photoluminescence from iron ions in crystals","authors":"Qiaoling Chen, Qianshan Quan, Chang-Kui Duan","doi":"10.1103/physrevmaterials.8.095201","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.095201","url":null,"abstract":"The poor understanding of the optical transitions and luminescent mechanisms critically hindered the development of near-infrared (NIR) <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>Fe</mi></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math>-activated phosphors, and efficient luminescence from Fe(Oh) has rarely been reported. In our study, we delve into these challenges and realize their correlation with the quenching mechanism of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>Fe</mi></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math> luminescence. First-principles calculations are utilized to analyze energy levels and electron-phonon coupling parameters, further elucidating potential deactivation pathways and factors influencing the occurrence of photoluminescence. A heuristic rule based on ligand-field strength, determined by the absorption wavelength of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>Cr</mi></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math> occupying the same octahedral site in oxides, is proposed to facilitate the prediction of both the potential and wavelength of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>Fe</mi></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math> emission. Our study offers consistent and reliable interpretations for the difficulties and challenges of iron-doped crystals, and provides valuable insights on the design and optimization of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>Fe</mi></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math>-based phosphors.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"30 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-06DOI: 10.1103/physrevmaterials.8.093602
A. Zafar, A. M. Milinda Abeykoon, V. Petkov
The structural mechanism of the magnetic phase transitions in ilmenite, including the paramagnetic (PM) to antiferromagnetic (AFM) transition induced by reducing temperature in zero magnetic field and the AFM to ferromagnetic (FM) transition induced by applying strong magnetic field at a fixed temperature below the Néel temperature, , are studied by total synchrotron x-ray scattering. It is found that in both cases the concerted effect of Coulomb repulsion, spin-orbit coupling, and exchange interactions is what determines the response of the crystal lattice to variations in external perturbations such as temperature and magnetic field. In particular, due to strong spin-orbit coupling and Coulomb repulsion, Fe and Ti atoms move in sync along the axis of the crystal lattice such that their separation changes by less than 1%. At the same time, due to strong intralayer ferromagnetic interactions, the Fe-O-Fe bond angle becomes closer to . Notably, the direction of the motion occuring during the temperature-induced PM to AFM transition is opposite to that occuring during the magnetic field-induced AFM to FM transition. Altogether, the seemingly simple ilmenite behaves like a complex physical system where charge, spin, orbital, and lattice degrees of freedom are strongly coupled. Our findings are likely to be relevant to other members of the ilmenite family and spin-orbit coupled magnetic insulators in general.
通过全同步加速器 X 射线散射研究了 FeTiO3 钛铁矿中磁性相变的结构机制，包括在零磁场中降低温度诱导的顺磁（PM）到反铁磁（AFM）转变，以及在低于奈尔温度 TN 的固定温度下施加强磁场诱导的反铁磁到铁磁（FM）转变。研究发现，在这两种情况下，库仑斥力、自旋轨道耦合和交换相互作用的协同效应决定了晶格对温度和磁场等外部扰动变化的响应。特别是，由于自旋轨道耦合和库仑斥力很强，铁原子和钛原子沿晶格的 c 轴同步移动，因此它们之间的距离变化不到 1%。同时，由于强烈的层内铁磁相互作用，Fe-O-Fe 键角变得更接近 90∘。值得注意的是，温度诱导的 PM 向 AFM 转变过程中发生的运动方向与磁场诱导的 AFM 向 FM 转变过程中发生的运动方向相反。总之，看似简单的 FeTiO3 钛铁矿表现得就像一个复杂的物理系统，其中电荷、自旋、轨道和晶格自由度紧密耦合。我们的发现可能与钛铁矿家族的其他成员以及一般自旋轨道耦合磁绝缘体有关。
{"title":"Structural mechanism of the magnetic phase transitions in FeTiO3","authors":"A. Zafar, A. M. Milinda Abeykoon, V. Petkov","doi":"10.1103/physrevmaterials.8.093602","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093602","url":null,"abstract":"The structural mechanism of the magnetic phase transitions in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>FeTiO</mi><mn>3</mn></msub></math> ilmenite, including the paramagnetic (PM) to antiferromagnetic (AFM) transition induced by reducing temperature in zero magnetic field and the AFM to ferromagnetic (FM) transition induced by applying strong magnetic field at a fixed temperature below the Néel temperature, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">N</mi></msub></math>, are studied by total synchrotron x-ray scattering. It is found that in both cases the concerted effect of Coulomb repulsion, spin-orbit coupling, and exchange interactions is what determines the response of the crystal lattice to variations in external perturbations such as temperature and magnetic field. In particular, due to strong spin-orbit coupling and Coulomb repulsion, Fe and Ti atoms move in sync along the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>c</mi></math> axis of the crystal lattice such that their separation changes by less than 1%. At the same time, due to strong intralayer ferromagnetic interactions, the Fe-O-Fe bond angle becomes closer to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>90</mn><mo>∘</mo></msup></math>. Notably, the direction of the motion occuring during the temperature-induced PM to AFM transition is opposite to that occuring during the magnetic field-induced AFM to FM transition. Altogether, the seemingly simple <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>FeTiO</mi><mn>3</mn></msub></math> ilmenite behaves like a complex physical system where charge, spin, orbital, and lattice degrees of freedom are strongly coupled. Our findings are likely to be relevant to other members of the ilmenite family and spin-orbit coupled magnetic insulators in general.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"2 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-05DOI: 10.1103/physrevmaterials.8.093601
Jayden Plumb, Andrea Capa Salinas, Krishnanand Mallayya, Elliot Kisiel, Fellipe B. Carneiro, Reina Gomez, Ganesh Pokharel, Eun-Ah Kim, Suchismita Sarker, Zahirul Islam, Sam Daly, Stephen D. Wilson
We present x-ray scattering studies resolving structural twinning and phase separation in the charge density wave (CDW) state of the kagome superconductor . The three-dimensional CDW state in is reported to form a complex superposition of Star of David (SoD) or Tri-Hexagonal (TrH) patterns of distortion within its kagome planes, but the out-of-plane stacking is marked by metastability. To resolve the impact of this metastability, we present reciprocal space mapping and real-space images of collected across multiple length scales using temperature-dependent high-dynamic range mapping (HDRM) and dark-field x-ray microscopy (DFXM). The experimental data provide evidence for a rich microstructure that forms in the CDW state. Data evidence metastability in the formation of and CDW supercells dependent on thermal history and mechanical deformation. We further directly resolve the real space phase segregation of both supercells, as well as a real-space, structural twinning driven by the broken rotational symmetry of the CDW state. Our combined results provide insights into the role of microstructure and twinning in experiments probing the electronic properties of where rotational symmetry is broken by the three-dimensional charge density wave order but locally preserved for any single kagome layer.
{"title":"Phase-separated charge order and twinning across length scales in CsV3Sb5","authors":"Jayden Plumb, Andrea Capa Salinas, Krishnanand Mallayya, Elliot Kisiel, Fellipe B. Carneiro, Reina Gomez, Ganesh Pokharel, Eun-Ah Kim, Suchismita Sarker, Zahirul Islam, Sam Daly, Stephen D. Wilson","doi":"10.1103/physrevmaterials.8.093601","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093601","url":null,"abstract":"We present x-ray scattering studies resolving structural twinning and phase separation in the charge density wave (CDW) state of the kagome superconductor <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>CsV</mi><mn>3</mn></msub><msub><mi>Sb</mi><mn>5</mn></msub></mrow></math>. The three-dimensional CDW state in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>CsV</mi><mn>3</mn></msub><msub><mi>Sb</mi><mn>5</mn></msub></mrow></math> is reported to form a complex superposition of Star of David (SoD) or Tri-Hexagonal (TrH) patterns of distortion within its kagome planes, but the out-of-plane stacking is marked by metastability. To resolve the impact of this metastability, we present reciprocal space mapping and real-space images of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>CsV</mi><mn>3</mn></msub><msub><mi>Sb</mi><mn>5</mn></msub></mrow></math> collected across multiple length scales using temperature-dependent high-dynamic range mapping (HDRM) and dark-field x-ray microscopy (DFXM). The experimental data provide evidence for a rich microstructure that forms in the CDW state. Data evidence metastability in the formation of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>2</mn><mo>×</mo><mn>2</mn><mo>×</mo><mn>4</mn></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>2</mn><mo>×</mo><mn>2</mn><mo>×</mo><mn>2</mn></mrow></math> CDW supercells dependent on thermal history and mechanical deformation. We further directly resolve the real space phase segregation of both supercells, as well as a real-space, structural twinning driven by the broken rotational symmetry of the CDW state. Our combined results provide insights into the role of microstructure and twinning in experiments probing the electronic properties of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>CsV</mi><mn>3</mn></msub><msub><mi>Sb</mi><mn>5</mn></msub></mrow></math> where rotational symmetry is broken by the three-dimensional charge density wave order but locally preserved for any single kagome layer.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"28 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-05DOI: 10.1103/physrevmaterials.8.094403
Lucile Féger, Carlos Escorihuela-Sayalero, Jean-Michel Rampnoux, Kyriaki Kontou, Micka Bah, Jorge Íñiguez-González, Claudio Cazorla, Isabelle Monot-Laffez, Sarah Douri, Stéphane Grauby, Riccardo Rurali, Stefan Dilhaire, Séverine Gomès, Guillaume F. Nataf
Materials with on-demand control of thermal conductivity are the prerequisites to build thermal conductivity switches, where the thermal conductivity can be turned on and off. However, the ideal switch, while required to develop novel approaches to solid-state refrigeration, energy harvesting, and even phononic circuits, is still missing. It should consist of an active material only, be environment friendly, and operate near room temperature with a reversible, fast, and large switching ratio. Here, we first predict by ab initio electronic structure calculations that ferroelectric domains in barium titanate exhibit anisotropic thermal conductivities. We confirm this prediction by combining frequency-domain thermoreflectance and scanning thermal microscopy measurements on a single crystal of barium titanate. We then use this gained knowledge to propose a lead-free thermal conductivity switch without inactive material, operating reversibly with an electric field. At room temperature, we find a switching ratio of , exceeding the performances of state-of-the-art materials suggested for thermal conductivity switches.
按需控制热导率的材料是制造热导率开关的先决条件，在这种开关中，热导率可以开启或关闭。然而，理想的开关虽然是开发固态制冷、能量收集甚至声波电路的新方法所必需的，但目前仍然缺失。它应该只由活性材料组成，对环境友好，在室温附近工作，具有可逆、快速和大开关比。在这里，我们首先通过ab initio 电子结构计算预测钛酸钡中的铁电畴会表现出各向异性的热导率。通过对钛酸钡单晶体进行频域热反射和扫描热显微镜测量，我们证实了这一预测。然后，我们利用这些知识提出了一种无铅导热开关，它不含非活性材料，在电场作用下可逆运行。在室温下，我们发现开关比为 1.6±0.3，超过了建议用于导热开关的最先进材料的性能。
{"title":"Lead-free room-temperature ferroelectric thermal conductivity switch using anisotropies in thermal conductivities","authors":"Lucile Féger, Carlos Escorihuela-Sayalero, Jean-Michel Rampnoux, Kyriaki Kontou, Micka Bah, Jorge Íñiguez-González, Claudio Cazorla, Isabelle Monot-Laffez, Sarah Douri, Stéphane Grauby, Riccardo Rurali, Stefan Dilhaire, Séverine Gomès, Guillaume F. Nataf","doi":"10.1103/physrevmaterials.8.094403","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094403","url":null,"abstract":"Materials with on-demand control of thermal conductivity are the prerequisites to build thermal conductivity switches, where the thermal conductivity can be turned <span>on</span> and <span>off</span>. However, the ideal switch, while required to develop novel approaches to solid-state refrigeration, energy harvesting, and even phononic circuits, is still missing. It should consist of an active material only, be environment friendly, and operate near room temperature with a reversible, fast, and large switching ratio. Here, we first predict by <i>ab initio</i> electronic structure calculations that ferroelectric domains in barium titanate exhibit anisotropic thermal conductivities. We confirm this prediction by combining frequency-domain thermoreflectance and scanning thermal microscopy measurements on a single crystal of barium titanate. We then use this gained knowledge to propose a lead-free thermal conductivity switch without inactive material, operating reversibly with an electric field. At room temperature, we find a switching ratio of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1.6</mn><mo>±</mo><mn>0.3</mn></mrow></math>, exceeding the performances of state-of-the-art materials suggested for thermal conductivity switches.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"12 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142226372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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