Pub Date : 2026-02-04DOI: 10.1038/s41535-026-00859-7
Marvin Kopp, Charu Garg, Sarah Krebber, Kristin Kliemt, Cornelius Krellner, Sudhaman R. Balguri, Mira Mahendru, Fazel Tafti, Theodore L. Breeze, Nathan P. Bentley, Francis L. Pratt, Thomas J. Hicken, Hubertus Luetkens, Jonas A. Krieger, Stephen J. Blundell, Tom Lancaster, M. Victoria Ale Crivillero, Steffen Wirth, Jens Müller
The interplay between magnetism and charge transport is central to understanding colossal magnetoresistance (CMR), a phenomenon well studied in ferromagnets. Recently, antiferromagnetic (AFM) EuCd 2 P 2 has attracted considerable interest due to its remarkable CMR, for which magnetic fluctuations and the formation of ferromagnetic clusters have been proposed as key mechanisms. Here we provide direct evidence that these effects originate from the formation and percolation of magnetic polarons. We employ a complementary set of sensitive probes that allows for a direct comparison of electronic and magnetic properties on multiple time scales revealing pronounced electronic and magnetic phase separation below T* ≈ 2 TN . These measurements indicate an inhomogeneous, percolating electronic system below T* and well above the magnetic ordering temperature TN = 11 K. In applied magnetic fields, the onset of the pronounced negative MR in the paramagnetic regime emerges at a universal critical magnetization. The characteristic size of the magnetic polarons near the percolation threshold is estimated to be ~6−10 nm. Our results establish dynamic polaron percolation within an AFM matrix as the microscopic origin of CMR in EuCd 2 P 2 , providing a unified framework for magnetotransport in Eu-based correlated semiconductors.
{"title":"Robust magnetic polaron percolation in the antiferromagnetic CMR system EuCd2P2","authors":"Marvin Kopp, Charu Garg, Sarah Krebber, Kristin Kliemt, Cornelius Krellner, Sudhaman R. Balguri, Mira Mahendru, Fazel Tafti, Theodore L. Breeze, Nathan P. Bentley, Francis L. Pratt, Thomas J. Hicken, Hubertus Luetkens, Jonas A. Krieger, Stephen J. Blundell, Tom Lancaster, M. Victoria Ale Crivillero, Steffen Wirth, Jens Müller","doi":"10.1038/s41535-026-00859-7","DOIUrl":"https://doi.org/10.1038/s41535-026-00859-7","url":null,"abstract":"The interplay between magnetism and charge transport is central to understanding colossal magnetoresistance (CMR), a phenomenon well studied in ferromagnets. Recently, antiferromagnetic (AFM) EuCd <jats:sub>2</jats:sub> P <jats:sub>2</jats:sub> has attracted considerable interest due to its remarkable CMR, for which magnetic fluctuations and the formation of ferromagnetic clusters have been proposed as key mechanisms. Here we provide direct evidence that these effects originate from the formation and percolation of magnetic polarons. We employ a complementary set of sensitive probes that allows for a direct comparison of electronic and magnetic properties on multiple time scales revealing pronounced electronic and magnetic phase separation below <jats:italic>T</jats:italic> <jats:sup>*</jats:sup> ≈ 2 <jats:italic>T</jats:italic> <jats:sub> <jats:italic>N</jats:italic> </jats:sub> . These measurements indicate an inhomogeneous, percolating electronic system below <jats:italic>T</jats:italic> <jats:sup>*</jats:sup> and well above the magnetic ordering temperature <jats:italic>T</jats:italic> <jats:sub> <jats:italic>N</jats:italic> </jats:sub> = 11 K. In applied magnetic fields, the onset of the pronounced negative MR in the paramagnetic regime emerges at a universal critical magnetization. The characteristic size of the magnetic polarons near the percolation threshold is estimated to be ~6−10 nm. Our results establish dynamic polaron percolation within an AFM matrix as the microscopic origin of CMR in EuCd <jats:sub>2</jats:sub> P <jats:sub>2</jats:sub> , providing a unified framework for magnetotransport in Eu-based correlated semiconductors.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"22 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146115719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-31DOI: 10.1038/s41535-026-00851-1
Chaebin Kim, Olivia Vilella, Youjin Lee, Pyeongjae Park, Yeochan An, Woonghee Cho, Matthew B. Stone, Alexander I. Kolesnikov, Yiqing Hao, Shinichiro Asai, Shinichi Itoh, Takatsugu Masuda, Sakib Matin, Yuna Kim, Sung-Jin Kim, Martin Mourigal, Je-Geun Park
Topological spin textures are a spectacular manifestation of the chirality of the magnetic nanostructures protected by topology. Most known skyrmion systems are restricted to a topological charge of one, require an external magnetic field for stabilization, and are only reported in a few materials. Here, we investigate the possibility that the Kitaev anisotropic-exchange interaction stabilizes a higher-order skyrmion crystal in the insulating van der Waals magnet NiI2. We unveil and explain the incommensurate static and dynamic magnetic correlations across three temperature-driven magnetic phases of this compound using neutron scattering measurements, simulations, and modeling. Our parameter optimisation yields a minimal Kitaev-Heisenberg Hamiltonian for NiI2 which reproduces the experimentally observed magnetic excitations. Monte Carlo simulations for this model predict the emergence of the higher-order skyrmion crystal but neutron diffraction and optical experiments in the candidate intermediate temperature regime are inconclusive. We discuss possible deviations from the Kitaev-Heisenberg model that explains our results and conclude that NiI2, in addition to multiferroic properties in the bulk and few-layer limits, is a Kitaev bulk material proximate to the finite temperature higher-order skyrmion crystal phase.
{"title":"Kitaev interaction and proximate higher-order skyrmion crystal in the triangular lattice van der Waals antiferromagnet NiI2","authors":"Chaebin Kim, Olivia Vilella, Youjin Lee, Pyeongjae Park, Yeochan An, Woonghee Cho, Matthew B. Stone, Alexander I. Kolesnikov, Yiqing Hao, Shinichiro Asai, Shinichi Itoh, Takatsugu Masuda, Sakib Matin, Yuna Kim, Sung-Jin Kim, Martin Mourigal, Je-Geun Park","doi":"10.1038/s41535-026-00851-1","DOIUrl":"https://doi.org/10.1038/s41535-026-00851-1","url":null,"abstract":"Topological spin textures are a spectacular manifestation of the chirality of the magnetic nanostructures protected by topology. Most known skyrmion systems are restricted to a topological charge of one, require an external magnetic field for stabilization, and are only reported in a few materials. Here, we investigate the possibility that the Kitaev anisotropic-exchange interaction stabilizes a higher-order skyrmion crystal in the insulating van der Waals magnet NiI2. We unveil and explain the incommensurate static and dynamic magnetic correlations across three temperature-driven magnetic phases of this compound using neutron scattering measurements, simulations, and modeling. Our parameter optimisation yields a minimal Kitaev-Heisenberg Hamiltonian for NiI2 which reproduces the experimentally observed magnetic excitations. Monte Carlo simulations for this model predict the emergence of the higher-order skyrmion crystal but neutron diffraction and optical experiments in the candidate intermediate temperature regime are inconclusive. We discuss possible deviations from the Kitaev-Heisenberg model that explains our results and conclude that NiI2, in addition to multiferroic properties in the bulk and few-layer limits, is a Kitaev bulk material proximate to the finite temperature higher-order skyrmion crystal phase.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"8 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146089891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-22DOI: 10.1038/s41535-026-00849-9
Thomas A. Maier, Peter Doak, Ling-Fang Lin, Yang Zhang, Adriana Moreo, Elbio Dagotto
The discovery of <jats:italic>T</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub> ~ 80 K superconductivity in pressurized La <jats:sub>3</jats:sub> Ni <jats:sub>2</jats:sub> O <jats:sub>7</jats:sub> has launched a new platform to study high-temperature superconductivity. Using non-perturbative dynamic cluster approximation quantum Monte Carlo calculations, we characterize the magnetic and superconducting pairing behavior of a realistic bilayer two-orbital Hubbard-Hund model of this system that describes the relevant Ni <jats:italic>e</jats:italic> <jats:sub> <jats:italic>g</jats:italic> </jats:sub> states with physically relevant interaction strengths. We find a leading <jats:italic>s</jats:italic> <jats:sup>±</jats:sup> superconducting instability in this model at a temperature <jats:italic>T</jats:italic> ~ 100 K close to the experimentally observed <jats:italic>T</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub> . Analyzing the orbital and spatial structure of the effective pairing interaction giving rise to this state reveals that the interaction predominantly acts between local interlayer pairs of the <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${d}_{3{z}^{2}-{r}^{2}}$$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:msup> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>-</mml:mo> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:math> </jats:alternatives> </jats:inline-formula> orbital. By correlating the strength of the interaction with that of the magnetic spin fluctuations we show that it is driven by strong interlayer spin-fluctuations arising from the <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${d}_{3{z}^{2}-{r}^{2}}$$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:msup> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>-</mml:mo> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:math> </jats:alternatives> </jats:inline-formula> orbital. These results provide first-time non-perturbative evidence supporting the picture that a simple single-orbital bilayer Hubbard model for the Ni <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${d}_{3{z}^{2}-{r}^{2}}$$</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:msup> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>-</mml:mo> <mml:msup> <mml:mrow> <mml:mi>r</m
{"title":"Interlayer pairing in bilayer nickelates","authors":"Thomas A. Maier, Peter Doak, Ling-Fang Lin, Yang Zhang, Adriana Moreo, Elbio Dagotto","doi":"10.1038/s41535-026-00849-9","DOIUrl":"https://doi.org/10.1038/s41535-026-00849-9","url":null,"abstract":"The discovery of <jats:italic>T</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub> ~ 80 K superconductivity in pressurized La <jats:sub>3</jats:sub> Ni <jats:sub>2</jats:sub> O <jats:sub>7</jats:sub> has launched a new platform to study high-temperature superconductivity. Using non-perturbative dynamic cluster approximation quantum Monte Carlo calculations, we characterize the magnetic and superconducting pairing behavior of a realistic bilayer two-orbital Hubbard-Hund model of this system that describes the relevant Ni <jats:italic>e</jats:italic> <jats:sub> <jats:italic>g</jats:italic> </jats:sub> states with physically relevant interaction strengths. We find a leading <jats:italic>s</jats:italic> <jats:sup>±</jats:sup> superconducting instability in this model at a temperature <jats:italic>T</jats:italic> ~ 100 K close to the experimentally observed <jats:italic>T</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub> . Analyzing the orbital and spatial structure of the effective pairing interaction giving rise to this state reveals that the interaction predominantly acts between local interlayer pairs of the <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${d}_{3{z}^{2}-{r}^{2}}$$</jats:tex-math> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:msup> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>-</mml:mo> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:math> </jats:alternatives> </jats:inline-formula> orbital. By correlating the strength of the interaction with that of the magnetic spin fluctuations we show that it is driven by strong interlayer spin-fluctuations arising from the <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${d}_{3{z}^{2}-{r}^{2}}$$</jats:tex-math> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:msup> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>-</mml:mo> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:math> </jats:alternatives> </jats:inline-formula> orbital. These results provide first-time non-perturbative evidence supporting the picture that a simple single-orbital bilayer Hubbard model for the Ni <jats:inline-formula> <jats:alternatives> <jats:tex-math>$${d}_{3{z}^{2}-{r}^{2}}$$</jats:tex-math> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:msup> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>-</mml:mo> <mml:msup> <mml:mrow> <mml:mi>r</m","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"101 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146033153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-20DOI: 10.1038/s41535-026-00852-0
Tristan R. Cao, Hengdi Zhao, Xudong Huai, Arabella Quane, Thao T. Tran, Feng Ye, Gang Cao
We demonstrate that applying modest magnetic fields (<0.1 T) during high-temperature crystal growth can profoundly alter the structure and ground state of a spin-orbit-coupled, antiferromagnetic trimer lattice. Using BaIrO₃ as a model system, whose ground state is intricately dictated by the trimer lattice, we show that magneto-synthesis, a field-assisted synthesis approach, stabilizes a structurally compressed, metastable metallic and magnetically suppressed phases inaccessible via conventional methods. These effects include a 0.85% reduction in unit cell, 4-order-of-magnitude decrease in resistivity, a 10-fold enhancement of the Sommerfeld coefficient, and the collapse of long-range magnetic order -- all intrinsic and bulk in origin. First-principles calculations confirm that the field-stabilized structure lies substantially above the ground state in energy, highlighting its metastable character. These large, coherent and correlated changes across multiple bulk properties, unlike those caused by dilute impurities, defects or off-stoichiometry, point to an intrinsic field-induced mechanism. The findings establish magneto-synthesis as a powerful new pathway for accessing non-equilibrium quantum phases in strongly correlated materials.
{"title":"Field-tailoring quantum materials via magneto-synthesis: metastable metallic and magnetically suppressed phases in a trimer iridate","authors":"Tristan R. Cao, Hengdi Zhao, Xudong Huai, Arabella Quane, Thao T. Tran, Feng Ye, Gang Cao","doi":"10.1038/s41535-026-00852-0","DOIUrl":"https://doi.org/10.1038/s41535-026-00852-0","url":null,"abstract":"We demonstrate that applying modest magnetic fields (<0.1 T) during high-temperature crystal growth can profoundly alter the structure and ground state of a spin-orbit-coupled, antiferromagnetic trimer lattice. Using BaIrO₃ as a model system, whose ground state is intricately dictated by the trimer lattice, we show that magneto-synthesis, a field-assisted synthesis approach, stabilizes a structurally compressed, metastable metallic and magnetically suppressed phases inaccessible via conventional methods. These effects include a 0.85% reduction in unit cell, 4-order-of-magnitude decrease in resistivity, a 10-fold enhancement of the Sommerfeld coefficient, and the collapse of long-range magnetic order -- all intrinsic and bulk in origin. First-principles calculations confirm that the field-stabilized structure lies substantially above the ground state in energy, highlighting its metastable character. These large, coherent and correlated changes across multiple bulk properties, unlike those caused by dilute impurities, defects or off-stoichiometry, point to an intrinsic field-induced mechanism. The findings establish magneto-synthesis as a powerful new pathway for accessing non-equilibrium quantum phases in strongly correlated materials.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"45 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-19DOI: 10.1038/s41535-025-00831-x
Wenfeng Wu, Eric Jacob, Viktor Christiansson, Ying Gao, Zhi Zeng, Karsten Held, Liang Si
Recent experimental discoveries of infinite- and finite-layer nickelate superconductors have highlighted the importance of a single-band {d}_{{x}^{2}-{y}^{2}}{d}_{{x}^{2}-{y}^{2}} Fermi surface for enabling unconventional superconductivity similar to cuprates. Motivated by this, we use density functional theory (DFT) and dynamical mean-field theory (DMFT) to identify two infinite-layer fluorides—KNiF2 and KPdF2—as promising candidates. Both materials exhibit strong correlations, structural stability, a single-band {d}_{{x}^{2}-{y}^{2}}{d}_{{x}^{2}-{y}^{2}} Fermi surface, and an antiferromagnetic Mott insulating state for the undoped parent compound. However, in KNiF2, overly strong correlations suppress spin fluctuations, preventing the electron pairing and superconducting states at finite temperatures. In contrast, KPdF2 offers tunable superconducting behavior. Using dynamical vertex approximation (DΓA), we show that 20% hole doping on SrTiO3 and 10% electron doping on MgO substrate yield superconducting transition temperatures of 65 K and 63 K, respectively, demonstrating the material’s potential through doping and substrate engineering.
{"title":"Single-band fluorides akin to infinite-layer cuprate superconductors","authors":"Wenfeng Wu, Eric Jacob, Viktor Christiansson, Ying Gao, Zhi Zeng, Karsten Held, Liang Si","doi":"10.1038/s41535-025-00831-x","DOIUrl":"https://doi.org/10.1038/s41535-025-00831-x","url":null,"abstract":"Recent experimental discoveries of infinite- and finite-layer nickelate superconductors have highlighted the importance of a single-band {d}_{{x}^{2}-{y}^{2}}{d}_{{x}^{2}-{y}^{2}} Fermi surface for enabling unconventional superconductivity similar to cuprates. Motivated by this, we use density functional theory (DFT) and dynamical mean-field theory (DMFT) to identify two infinite-layer fluorides—KNiF2 and KPdF2—as promising candidates. Both materials exhibit strong correlations, structural stability, a single-band {d}_{{x}^{2}-{y}^{2}}{d}_{{x}^{2}-{y}^{2}} Fermi surface, and an antiferromagnetic Mott insulating state for the undoped parent compound. However, in KNiF2, overly strong correlations suppress spin fluctuations, preventing the electron pairing and superconducting states at finite temperatures. In contrast, KPdF2 offers tunable superconducting behavior. Using dynamical vertex approximation (DΓA), we show that 20% hole doping on SrTiO3 and 10% electron doping on MgO substrate yield superconducting transition temperatures of 65 K and 63 K, respectively, demonstrating the material’s potential through doping and substrate engineering.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"31 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-16DOI: 10.1038/s41535-026-00848-w
Kevin A. Smith, Yanhong Gu, Xianghan Xu, Heung-Sik Kim, Sang-Wook Cheong, Scott A. Crooker, Janice L. Musfeldt
Magnetoelectric multiferroics such as rare earth manganites host nonreciprocal behavior driven by low symmetry, spin-orbit coupling, and toroidal moments, although less has been done to explore whether lanthanides like Er3+ might extend functionality into the hard infrared for optical communications purposes. In this work, we reveal nonreciprocity in the f-manifold crystal field excitations of h-Lu0.9Er0.1MnO3. In addition to contrast in the highest fields, we demonstrate nonreciprocity at technologically-relevant energy scales--specifically in the E-, S-, and C-bands of the telecom wavelength range--and at low magnetic fields and room temperature. In fact, the low field behavior is consistent with possible altermagnetism. These findings advance the overall understanding of localized excitations in rare earth-containing systems and pave the way for entirely new types of telecom applications.
{"title":"Optical diode effect at telecom wavelengths in a polar magnet","authors":"Kevin A. Smith, Yanhong Gu, Xianghan Xu, Heung-Sik Kim, Sang-Wook Cheong, Scott A. Crooker, Janice L. Musfeldt","doi":"10.1038/s41535-026-00848-w","DOIUrl":"https://doi.org/10.1038/s41535-026-00848-w","url":null,"abstract":"Magnetoelectric multiferroics such as rare earth manganites host nonreciprocal behavior driven by low symmetry, spin-orbit coupling, and toroidal moments, although less has been done to explore whether lanthanides like Er3+ might extend functionality into the hard infrared for optical communications purposes. In this work, we reveal nonreciprocity in the f-manifold crystal field excitations of h-Lu0.9Er0.1MnO3. In addition to contrast in the highest fields, we demonstrate nonreciprocity at technologically-relevant energy scales--specifically in the E-, S-, and C-bands of the telecom wavelength range--and at low magnetic fields and room temperature. In fact, the low field behavior is consistent with possible altermagnetism. These findings advance the overall understanding of localized excitations in rare earth-containing systems and pave the way for entirely new types of telecom applications.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"85 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145993481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-16DOI: 10.1038/s41535-026-00850-2
Daria I. Markina, Priyanka Mondal, Lukas Krelle, Sai Shradha, Mikhail M. Glazov, Regine von Klitzing, Kseniia Mosina, Zdenek Sofer, Bernhard Urbaszek
The van der Waals antiferromagnet CrSBr exhibits coupling of vibrational, electronic, and magnetic degrees of freedom, giving rise to distinctive quasi-particle interactions. We investigate these interactions across a wide temperature range using polarization-resolved Raman spectroscopy at various excitation energies, complemented by optical absorption and photoluminescence excitation (PLE) spectroscopy. Under 1.96 eV excitation, we observe pronounced changes in the ({A}_{g}^{1}), ({A}_{g}^{2}), and ({A}_{g}^{3}) Raman modes near the Néel temperature, coinciding with modifications in the oscillator strength of excitonic transitions and clear resonances in PLE. The distinct temperature evolution of Raman tensor elements and polarization anisotropy of Raman modes indicates that they couple to different excitonic and electronic states. The suppression of the excitonic states' oscillation strength above the Néel temperature could be related to the magnetic phase transition, thereby connecting these excitonic states and Raman modes to a specific spin alignment. We develop a simple model that describes how magnetic order impacts excitonic states and hence the intensity and polarization of the Raman scattering signal. These observations make CrSBr a versatile platform for probing quasi-particle interactions in low-dimensional magnets and provide insights for applications in quantum sensing and quantum communication.
{"title":"Interplay of vibrational, electronic, and magnetic states in CrSBr","authors":"Daria I. Markina, Priyanka Mondal, Lukas Krelle, Sai Shradha, Mikhail M. Glazov, Regine von Klitzing, Kseniia Mosina, Zdenek Sofer, Bernhard Urbaszek","doi":"10.1038/s41535-026-00850-2","DOIUrl":"https://doi.org/10.1038/s41535-026-00850-2","url":null,"abstract":"The van der Waals antiferromagnet CrSBr exhibits coupling of vibrational, electronic, and magnetic degrees of freedom, giving rise to distinctive quasi-particle interactions. We investigate these interactions across a wide temperature range using polarization-resolved Raman spectroscopy at various excitation energies, complemented by optical absorption and photoluminescence excitation (PLE) spectroscopy. Under 1.96 eV excitation, we observe pronounced changes in the ({A}_{g}^{1}), ({A}_{g}^{2}), and ({A}_{g}^{3}) Raman modes near the Néel temperature, coinciding with modifications in the oscillator strength of excitonic transitions and clear resonances in PLE. The distinct temperature evolution of Raman tensor elements and polarization anisotropy of Raman modes indicates that they couple to different excitonic and electronic states. The suppression of the excitonic states' oscillation strength above the Néel temperature could be related to the magnetic phase transition, thereby connecting these excitonic states and Raman modes to a specific spin alignment. We develop a simple model that describes how magnetic order impacts excitonic states and hence the intensity and polarization of the Raman scattering signal. These observations make CrSBr a versatile platform for probing quasi-particle interactions in low-dimensional magnets and provide insights for applications in quantum sensing and quantum communication.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"38 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145993492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Yttrium iron garnet (YIG) film, especially with perpendicular magnetic anisotropy (PMA), is a promising material for energy-efficient spintronic devices due to its extremely low damping constant. However, a poorly crystallized layer tends to form on the top surface of the YIG film during the annealing process, which severely hinders the interfacial spin transport. To overcome this limitation, we developed a surface treatment method using soft phosphoric acid. After the surface wet-etching treatment, both the spin mixing conductance and interfacial thermal conductance between the PMA-YIG film and post-deposited Pt layer can be increased by ~70% and ~100%, respectively. These PMA-YIG films with wet-etched surfaces hold promise for ultrahigh-density spintronic device applications.
{"title":"Surface wet-etched Y3Fe5O12 films with perpendicular magnetic anisotropy for ultrahigh density spintronic device applications","authors":"Shuyao Chen, Mingqian Yuan, Qixun Guo, Yunfei Xie, Dengfu Deng, Jiayi Zheng, Lintong Huang, Donghua Liu, Xuejun Yan, Ming-Hui Lu, Yan-Feng Chen, Tao Liu","doi":"10.1038/s41535-026-00847-x","DOIUrl":"https://doi.org/10.1038/s41535-026-00847-x","url":null,"abstract":"Yttrium iron garnet (YIG) film, especially with perpendicular magnetic anisotropy (PMA), is a promising material for energy-efficient spintronic devices due to its extremely low damping constant. However, a poorly crystallized layer tends to form on the top surface of the YIG film during the annealing process, which severely hinders the interfacial spin transport. To overcome this limitation, we developed a surface treatment method using soft phosphoric acid. After the surface wet-etching treatment, both the spin mixing conductance and interfacial thermal conductance between the PMA-YIG film and post-deposited Pt layer can be increased by ~70% and ~100%, respectively. These PMA-YIG films with wet-etched surfaces hold promise for ultrahigh-density spintronic device applications.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"14 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-01-12DOI: 10.1038/s41535-025-00844-6
Linda Ye, Jorge I. Facio, Madhav Prasad Ghimire, Mun K. Chan, Jhih-Shih You, David C. Bell, Manuel Richter, Jeroen van den Brink, Joseph G. Checkelsky
We report a study of Shubnikov–de Haas oscillations in high-quality single crystals of ferromagnetic Weyl semimetal Co3Sn2S2. The Fermi surfaces resolved in our experiments are three-dimensional and reflect an underlying trigonal crystallographic symmetry. Combined with density functional calculations, we identify that multiple Fermi surfaces in the system—of both electron and hole nature—arise from the energy dispersion of the (spin-orbit gapped) mirror-protected nodal rings. We observe an evolution of the Fermi surfaces with in-plane magnetic fields, in contrast to field perpendicular to the kagome lattice planes, which has little effect. Viewed alongside the easy-axis anisotropy of the system, our observation reveals an evolution of the electronic structure of Co3Sn2S2—including the Weyl points—with the ferromagnetic moment orientation. Through the case study of Co3Sn2S2, our results provide concrete experimental evidence of an anisotropic interplay via spin-orbit coupling between the magnetic degrees of freedom and electronic band singularities, which has long been expected in semimetallic and metallic magnetic systems.
{"title":"Magnetization orientation-dependent Shubnikov-de Haas oscillations in ferromagnetic Weyl semimetal Co3Sn2S2","authors":"Linda Ye, Jorge I. Facio, Madhav Prasad Ghimire, Mun K. Chan, Jhih-Shih You, David C. Bell, Manuel Richter, Jeroen van den Brink, Joseph G. Checkelsky","doi":"10.1038/s41535-025-00844-6","DOIUrl":"https://doi.org/10.1038/s41535-025-00844-6","url":null,"abstract":"We report a study of Shubnikov–de Haas oscillations in high-quality single crystals of ferromagnetic Weyl semimetal Co3Sn2S2. The Fermi surfaces resolved in our experiments are three-dimensional and reflect an underlying trigonal crystallographic symmetry. Combined with density functional calculations, we identify that multiple Fermi surfaces in the system—of both electron and hole nature—arise from the energy dispersion of the (spin-orbit gapped) mirror-protected nodal rings. We observe an evolution of the Fermi surfaces with in-plane magnetic fields, in contrast to field perpendicular to the kagome lattice planes, which has little effect. Viewed alongside the easy-axis anisotropy of the system, our observation reveals an evolution of the electronic structure of Co3Sn2S2—including the Weyl points—with the ferromagnetic moment orientation. Through the case study of Co3Sn2S2, our results provide concrete experimental evidence of an anisotropic interplay via spin-orbit coupling between the magnetic degrees of freedom and electronic band singularities, which has long been expected in semimetallic and metallic magnetic systems.","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"83 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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