Ferreira-Carvalho, M. M.; Rößler, S.; Chang, C. F.; Hu, Z.; Valvidares, S. M.; Gargiani, P.; Haverkort, M. W.; Mukharjee, P. K.; Gegenwart, P.; Tsirlin, A. A.; Tjeng, L. H. Trigonal distortion in the Kitaev candidate honeycomb magnet BaCo2(AsO4)2 Journal Article Phys. Rev. B 112, 125135 (2025). @article{ferreira-carvalho_trigonal_2025,
title = {Trigonal distortion in the Kitaev candidate honeycomb magnet BaCo_{2}(AsO_{4})_{2}},
author = {M. M. Ferreira-Carvalho and S. Rößler and C. F. Chang and Z. Hu and S. M. Valvidares and P. Gargiani and M. W. Haverkort and P. K. Mukharjee and P. Gegenwart and A. A. Tsirlin and L. H. Tjeng},
url = {https://link.aps.org/doi/10.1103/2sdd-pyx1},
doi = {10.1103/2sdd-pyx1},
year = {2025},
date = {2025-09-16},
urldate = {2025-09-01},
journal = {Phys. Rev. B},
volume = {112},
number = {12},
pages = {125135},
abstract = {We conducted x-ray absorption (XAS) and magnetic circular dichroism (XMCD) measurements at the Co 𝐿2,3 edges on single crystals of the Kitaev candidate honeycomb lattice compound BaCo2(AsO4)2. The measurements employed the inverse partial fluorescence yield technique, which is ideal for acquiring reliable x-ray absorption spectra from highly insulating samples, enabling precise quantitative analysis. Our experimental results revealed a significant linear dichroic signal, indicating strong trigonal distortion in the CoO6 octahedra in BaCo2(AsO4)2. We performed a detailed analysis of the experimental XAS and XMCD spectra using a full-multiplet configuration-interaction cluster model. This analysis unveiled that the 𝑡2𝑔 hole density is predominantly localized in the 𝑎1𝑔 orbital. Through XMCD sum rules and theoretical calculations, we quantified both the spin and orbital magnetic moments. Our study demonstrates that the local electronic structure of the CoO6 octahedra displays an effective trigonal distortion of approximately −0.114 eV. This distortion is larger than the Co 3𝑑 spin-orbit coupling constant, emphasizing the crucial impact of local structural distortions on the electronic and magnetic properties of BaCo2(AsO4)2.},
keywords = {B1},
pubstate = {published},
tppubtype = {article}
}
We conducted x-ray absorption (XAS) and magnetic circular dichroism (XMCD) measurements at the Co 𝐿2,3 edges on single crystals of the Kitaev candidate honeycomb lattice compound BaCo2(AsO4)2. The measurements employed the inverse partial fluorescence yield technique, which is ideal for acquiring reliable x-ray absorption spectra from highly insulating samples, enabling precise quantitative analysis. Our experimental results revealed a significant linear dichroic signal, indicating strong trigonal distortion in the CoO6 octahedra in BaCo2(AsO4)2. We performed a detailed analysis of the experimental XAS and XMCD spectra using a full-multiplet configuration-interaction cluster model. This analysis unveiled that the 𝑡2𝑔 hole density is predominantly localized in the 𝑎1𝑔 orbital. Through XMCD sum rules and theoretical calculations, we quantified both the spin and orbital magnetic moments. Our study demonstrates that the local electronic structure of the CoO6 octahedra displays an effective trigonal distortion of approximately −0.114 eV. This distortion is larger than the Co 3𝑑 spin-orbit coupling constant, emphasizing the crucial impact of local structural distortions on the electronic and magnetic properties of BaCo2(AsO4)2. |
Sharma, S.; Chioncel, L.; Marco, I. Di Exploring strong electronic correlations in the breathing kagome metal Fe3Sn Journal Article Phys. Rev. B 111, 235127 (2025). @article{sharma_exploring_2025,
title = {Exploring strong electronic correlations in the breathing kagome metal Fe_{3}Sn},
author = {S. Sharma and L. Chioncel and I. Di Marco},
url = {https://link.aps.org/doi/10.1103/xmmr-mfv4},
doi = {10.1103/xmmr-mfv4},
year = {2025},
date = {2025-06-16},
urldate = {2025-06-16},
journal = {Phys. Rev. B},
volume = {111},
number = {23},
pages = {235127},
abstract = {Kagome metals have emerged as pivotal materials in condensed matter physics due to their unique geometric arrangement and intriguing electronic properties. Understanding the origin of magnetism in these materials, particularly in iron-rich Fe-Sn binary compounds such as Fe3Sn, holds a significant importance, as they represent potential candidates for permanent magnets with a high Curie temperature and a strong magnetic anisotropy. In the present study, we employ density functional theory and dynamical mean-field theory to analyze the electronic structure and magnetic properties of Fe3Sn. Our investigation reveals the presence of several nearly flat bands and Weyl nodes at low excitation energies. The inclusion of local correlation effects is shown to push these features even closer to the Fermi energy, which may be important for their manipulation via external stimuli. Regarding magnetism, the Hubbard-like interaction leads to an increase of orbital polarization at the expenses of a minor reduction of the spin moment. The magnetic anisotropy energy exhibits a strong dependence on the particular choice of the Coulomb interaction parameters. Additionally, our detailed analysis of the interatomic exchange interactions indicates a significant contribution from the antisymmetric exchange, i.e., the Dzyaloshinskii-Moriya interaction, which showcases the existence of magnetic chirality in the system. Overall, our investigation highlights a strong interplay between the flat bands near the Fermi level, the local Coulomb interaction, and the triangular geometry of the lattice, which plays a crucial role in driving the magnetic properties of this material.},
keywords = {A5},
pubstate = {published},
tppubtype = {article}
}
Kagome metals have emerged as pivotal materials in condensed matter physics due to their unique geometric arrangement and intriguing electronic properties. Understanding the origin of magnetism in these materials, particularly in iron-rich Fe-Sn binary compounds such as Fe3Sn, holds a significant importance, as they represent potential candidates for permanent magnets with a high Curie temperature and a strong magnetic anisotropy. In the present study, we employ density functional theory and dynamical mean-field theory to analyze the electronic structure and magnetic properties of Fe3Sn. Our investigation reveals the presence of several nearly flat bands and Weyl nodes at low excitation energies. The inclusion of local correlation effects is shown to push these features even closer to the Fermi energy, which may be important for their manipulation via external stimuli. Regarding magnetism, the Hubbard-like interaction leads to an increase of orbital polarization at the expenses of a minor reduction of the spin moment. The magnetic anisotropy energy exhibits a strong dependence on the particular choice of the Coulomb interaction parameters. Additionally, our detailed analysis of the interatomic exchange interactions indicates a significant contribution from the antisymmetric exchange, i.e., the Dzyaloshinskii-Moriya interaction, which showcases the existence of magnetic chirality in the system. Overall, our investigation highlights a strong interplay between the flat bands near the Fermi level, the local Coulomb interaction, and the triangular geometry of the lattice, which plays a crucial role in driving the magnetic properties of this material. |
Prodan, L.; Evans, D. M.; Sukhanov, A. S.; Nikitin, S. E.; Tsirlin, A. A.; Puntigam, L.; Rahn, M. C.; Chioncel, L.; Tsurkan, V.; Kézsmárki, I. Easy-cone state mediating the spin reorientation in the topological kagome magnet Fe3Sn2 Journal Article Phys. Rev. B 111, 184442 (2025). @article{prodan_easy-cone_2025,
title = {Easy-cone state mediating the spin reorientation in the topological kagome magnet Fe_{3}Sn_{2}},
author = {L. Prodan and D. M. Evans and A. S. Sukhanov and S. E. Nikitin and A. A. Tsirlin and L. Puntigam and M. C. Rahn and L. Chioncel and V. Tsurkan and I. Kézsmárki},
url = {https://link.aps.org/doi/10.1103/PhysRevB.111.184442},
doi = {10.1103/PhysRevB.111.184442},
year = {2025},
date = {2025-05-30},
urldate = {2025-05-30},
journal = {Phys. Rev. B},
volume = {111},
number = {18},
pages = {184442},
abstract = {We investigated temperature-driven spin reorientation (SR) in the itinerant kagome magnet Fe3Sn2 using high-resolution synchrotron x-ray diffraction, neutron diffraction, magnetometry, and magnetic force microscopy (MFM), further supported by phenomenological analysis. Our study reveals a crossover from the state with easy-plane anisotropy to the high-temperature state with uniaxial easy-axis anisotropy taking place between ∼40 and 130 K through an intermediate easy-cone (or tilted spin) state. This state, induced by the interplay between the anisotropy constants 𝐾1 and 𝐾2, is clearly manifested in the thermal evolution of the magnetic structure factor, which reveals a gradual change of the SR angle 𝜃 between 40 and 130 K. We also found that the SR is accompanied by a magnetoelastic effect. Zero-field MFM images across the SR range show a transformation in surface magnetic patterns from a dendritic structure at 120 K to domain-wall-dominated MFM contrast at 40 K. Our analysis suggests that the SR and associated microstructural transformations are the results of competing first- and second-order anisotropy constants.},
keywords = {A4},
pubstate = {published},
tppubtype = {article}
}
We investigated temperature-driven spin reorientation (SR) in the itinerant kagome magnet Fe3Sn2 using high-resolution synchrotron x-ray diffraction, neutron diffraction, magnetometry, and magnetic force microscopy (MFM), further supported by phenomenological analysis. Our study reveals a crossover from the state with easy-plane anisotropy to the high-temperature state with uniaxial easy-axis anisotropy taking place between ∼40 and 130 K through an intermediate easy-cone (or tilted spin) state. This state, induced by the interplay between the anisotropy constants 𝐾1 and 𝐾2, is clearly manifested in the thermal evolution of the magnetic structure factor, which reveals a gradual change of the SR angle 𝜃 between 40 and 130 K. We also found that the SR is accompanied by a magnetoelastic effect. Zero-field MFM images across the SR range show a transformation in surface magnetic patterns from a dendritic structure at 120 K to domain-wall-dominated MFM contrast at 40 K. Our analysis suggests that the SR and associated microstructural transformations are the results of competing first- and second-order anisotropy constants. |
