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157 results on '"Gukasov, Arsen"'

1. Neutron diffraction study of magnetism in van der Waals layered MnBi$_{2n}$Te$_{3n+1}$

Author

Ding, Lei, Hu, Chaowei, Feng, Erxi, Jiang, Chenyang, Kibalin, Iurii A., Gukasov, Arsen, Chi, MiaoFang, Ni, Ni, and Cao, Huibo

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science
Abstract

Two-dimensional van der Waals MnBi$_{2n}$Te$_{3n+1}$ (n = 1, 2, 3, 4) compounds have been recently found to be intrinsic magnetic topological insulators rendering quantum anomalous Hall effect and diverse topological states. Here, we summarize and compare the crystal and magnetic structures of this family, and discuss the effects of chemical composition on their magnetism. We found that a considerable fraction of Bi occupies at the Mn sites in MnBi$_{2n}$Te$_{3n+1}$ (n = 1, 2, 3, 4) while Mn is no detectable at the non-magnetic atomic sites within the resolution of neutron diffraction experiments. The occupancy of Mn monotonically decreases with the increase of n. The polarized neutron diffraction on the representative MnBi$_{4}$Te$_{7}$ reveals that its magnetization density is exclusively accumulated at the Mn site, in good agreement with the results from the unpolarized neutron diffraction. The defects of Bi at the Mn site naturally explain the continuously reduced saturated magnetic moments from n = 1 to n = 4. The experimentally estimated critical exponents of all the compounds generally suggest a three-dimensional character of magnetism. Our work provides material-specified structural parameters that may be useful for band structure calculations to understand the observed topological surface states and for designing quantum magnetic materials through chemical doping., Comment: 5 figures, typos corrected

Published
2020

2. Local magnetic anisotropy by polarized neutron powder diffraction: application of magnetically induced preferred crystallite orientation

Author

Kibalin, Iurii and Gukasov, Arsen

Subjects
Condensed Matter - Materials Science
Abstract

Polarized neutron diffraction allows to determine the local susceptibility tensor on the magnetic site both in single crystals and powders. It is widely used in the studies of single crystals, but it is still hardly applicable to a number of highly interesting powder materials, like molecular magnets or nanoscale systems because of the low luminosity of existing instruments and the absence of an appropriate data analysis software. We show that these difficulties can be overcome by using a large area detector in combination with the two-dimensional Rietveld method and powder samples with magnetically induced preferred crystallite orientation. This is demonstrated by revisiting two test powder compounds, namely, low anisotropy (soft) ferrimagnetic compound Fe3O4 and spin-ice compound Ho2Ti2O7 with high local anisotropy. The values of magnetic moments in Fe3O4 and the susceptibility tensors of Ho2Ti2O7 at various temperatures and fields were found in perfect agreement with these found earlier in single crystal experiments. The magnetically induced preferred crystallite orientation was used to study the local susceptibility of a single-molecule magnet Co([(CH3)2N]2CS)2Cl2. Hence, the studies of local magnetic anisotropy in powder systems might now become accessible., Comment: 9 pages, 7 figures

Published
2019
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3. Magnetization density distribution of Sr$_2$IrO$_4$: Deviation from a local $j_\text{eff}=1/2$ picture

Author

Jeong, Jaehong, Lenz, Benjamin, Gukasov, Arsen, Fabreges, Xavier, Sazonov, Andrew, Hutanu, Vladimir, Louat, Alex, Bounoua, Dalila, Martins, Cyril, Biermann, Silke, Brouet, Véronique, Sidis, Yvan, and Bourges, Philippe

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

$5d$ iridium oxides are of huge interest due to the potential for new quantum states driven by strong spin-orbit coupling. The strontium iridate Sr$_2$IrO$_4$ is particularly in the spotlight because of the so-called $j_\text{eff}=1/2$ state consisting of a quantum superposition of the three local $t_{2g}$ orbitals with -- in its most simple version -- nearly equal population, which stabilizes an unconventional Mott insulating state. Here, we report an anisotropic and aspherical magnetization density distribution measured by polarized neutron diffraction in a magnetic field up to 5~T at 4~K, which strongly deviates from a local \jeffHalf picture even when distortion-induced deviations from the equal weights of the orbital populations are taken into account. Once reconstructed by the maximum entropy method and multipole expansion model refinement, the magnetization density shows cross-shaped positive four lobes along the crystallographic tetragonal axes with a large spatial extent, showing that the $xy$ orbital contribution is dominant. The analogy to the superconducting copper oxide systems might then be weaker than commonly thought., Comment: 3 figures + supplementary file included

Published
2019
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5. Antiferromagnetism and superconductivity in the half-Heusler semimetal HoPdBi

Author

Pavlosiuk, Orest, Kaczorowski, Dariusz, Fabreges, Xavier, Gukasov, Arsen, and Wiśniewski, Piotr

Subjects
Condensed Matter - Materials Science
Abstract

We observed the coexistence of superconductivity and antiferromagnetic order in the single-crystalline ternary pnictide HoPdBi, a plausible topological semimetal. The compound orders antiferromagnetically at $T_N =$1.9 K and exhibits superconductivity below $T_c =$0.7 K, which was confirmed by magnetic, electrical transport and specific heat measurements. The specific heat shows anomalies corresponding to antiferromagnetic ordering transition and crystalline field effect, but not to superconducting transition. Single-crystal neutron diffraction indicates that the antiferromagnetic structure is characterized by the (1/2, 1/2, 1/2) propagation vector. Temperature variation of the electrical resistivity reveals two parallel conducting channels of semiconducting and metallic character. In weak magnetic fields, the magnetoresistance exhibits weak antilocalization effect, while in strong fields and temperatures below 50 K it is large and negative. At temperatures below 7 K Shubnikov-de Haas oscillations with two frequencies appear in the resistivity. These oscillations have non-trivial Berry phase, which is a distinguished feature of Dirac fermions.

Published
2015
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6. Ethnopolitical Process in the North Caucasus Through the Lens of North Caucasian Online Media

Author

Kosov, Gennady V., Stankevich, Galina V., Gukasov, Arsen V., Romanko, Lyudmila V., Tekeeva, Madina U., Kacprzyk, Janusz, Series Editor, Pal, Nikhil R., Advisory Editor, Bello Perez, Rafael, Advisory Editor, Corchado, Emilio S., Advisory Editor, Hagras, Hani, Advisory Editor, Kóczy, László T., Advisory Editor, Kreinovich, Vladik, Advisory Editor, Lin, Chin-Teng, Advisory Editor, Lu, Jie, Advisory Editor, Melin, Patricia, Advisory Editor, Nedjah, Nadia, Advisory Editor, Nguyen, Ngoc Thanh, Advisory Editor, Wang, Jun, Advisory Editor, Popkova, Elena G., editor, and Ostrovskaya, Victoria N., editor

Published
2019
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7. Spin Density and Non-Collinear Magnetization in Frustrated Pyrochlore \tbti from Polarized Neutron Scattering

Author

Gukasov, Arsen, Cao, Huibo, Mirebeau, Isabelle, and Bonville, Pierre

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

We used a local susceptibility approach in extensive polarized neutron diffraction studies of the spin liquid \tbti. For a magnetic field applied along the [110] and [111] directions, we found that, at high temperature, all Tb moments are collinear and parallel to the field. With decreasing temperature, the Tb moments reorient from the field direction to their local anisotropy axes. For the [110] field direction, the field induced magnetic structure at 10 K is spin ice-like, but with two types of Tb moments of very different magnitudes. For a field along [111], the magnetic structure resembles the so-called "one in-three out" found in spin ices, with the difference that all Tb moments have an additional component along the [111] direction due to the magnetic field. The temperature evolution of the local susceptibilities clearly demonstrates a progressive change from Heisenberg to Ising behavior of the Tb moments when lowering the temperature, which appears to be a crystal field effect., Comment: Conference Proceeding of Polarized Neutrons in Condensed Matter Investigations (Tokai, Japan, 2008)

Published
2009
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10. Magnetic structure of the two-dimensional XY antiferromagnet Sr2CoSi2O7 studied using single-crystal neutron diffraction

Author

Dutta, Rajesh, primary, Thoma, Henrik, additional, Sazonov, Andrew, additional, Náfrádi, Bálint, additional, Meven, Martin, additional, Gukasov, Arsen, additional, Kocsis, Vilmos, additional, Zeitler, Uli, additional, Puri, Alessandro, additional, Tokunaga, Yusuke, additional, Taguchi, Yasujiro, additional, Tokura, Yoshinori, additional, Bordács, Sándor, additional, Kézsmárki, István, additional, and Hutanu, Vladimir, additional

Published
2023
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11. Multi-Technique Experimental Benchmarking of the Local Magnetic Anisotropy of a Cobalt(II) Single-Ion Magnet

Author

Gupta, Sandeep K., primary, Nielsen, Hannah H., additional, Thiel, Andreas M., additional, Klahn, Emil A., additional, Feng, Erxi, additional, Cao, Huibo B., additional, Hansen, Thomas C., additional, Lelièvre-Berna, Eddy, additional, Gukasov, Arsen, additional, Kibalin, Iurii, additional, Dechert, Sebastian, additional, Demeshko, Serhiy, additional, Overgaard, Jacob, additional, and Meyer, Franc, additional

Published
2023
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12. Magnetic structure of the two-dimensional XY antiferromagnet Sr2CoSi2O7 studied using single-crystal neutron diffraction

Author

Dutta, Rajesh, Thoma, Henrik, Sazonov, Andrew, Nafradi, Balint, Meven, Martin, Gukasov, Arsen, Kocsis, Vilmos, Zeitler, Uli, Puri, Alessandro, Tokunaga, Yusuke, Taguchi, Yasujiro, Tokura, Yoshinori, Bordacs, Sandor, Kezsmaerki, Istvan, and Hutanu, Vladimir

Subjects
ddc:530
Abstract

We report a combined polarized and unpolarized neutron diffraction study on a multiferroic Sr2CoSi2O7 (SCSO) single crystal below and above the antiferromagnetic ordering temperature TN = 6.5 K. Unpolarized neutron diffraction measurements at 15 K confirm the melilite-type tetragonal P4 over bar 21m space group as the parent structure of SCSO. The low temperature study at 2.3 K, in contrast, reveals symmetry lowering with the orthorhombic Cmm'2' and P212'12' magnetic space groups being equally possible. In these Cmm'2' and P212'12' magnetic space groups we obtain a very similar ordered magnetic moment about 2.86 and 2.94 mu B/Co2+, respectively, which lies in the ab plane. Our spin polarized flipping ratio measurements under an applied magnetic field of 6 T in the paramagnetic state support the results of our bulk magnetization data, indicating strong easy-plane spin anisotropy, responsible for the in-plane order below TN.

Published
2023

14. Magnetic order and sign of the Dzyaloshinskii-Moriya interaction in 2D antiferromagnet Ba2CoGe2O7 under applied magnetic field

Author

Thoma, Henrik, Hutanu, Vladimir, Dutta, Rajesh, Gukasov, Arsen, Kocsis, Vilmos, Tokunaga, Yusuke, Taguchi, Yasujiro, Tokura, Yoshinori, Kézsmárki, István, Roth, Georg, Angst, Manuel, Jülich Centre for Neutron Science (JCNS), Forschungszentrum Jülich GmbH at Heinz Maier-Leibnitz Zentrum (MLZ), Institute of Crystallography [Aachen], Rheinisch-Westfälische Technische Hochschule Aachen (RWTH), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, RIKEN Center for Emergent Matter Science, Wako 351-0198, Department of Physics, Budapest University of Technology and Economics and MTA-BME Condensed Matter Research Group, Budafoki ut 8, 1111 Budapest, Hungary, Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, The University of Tokyo (UTokyo), Department of Applied Physics, University of Tokyo, Kongo, Bunkyo-ku, Tokyo 113-8656, Department of Applied Physics, University of Tokyo, Hongo 7-3-1, Tokyo 113-8656, Experimentalphysik V, Center for Electronic Correlations and Magnetism, Institute for Physics, Universität Augsburg [Augsburg], Jülich Centre for Neutron Science (JCNS), Jülich Centre for Neutron Science (JCNS - PGI, JARA-FIT), Peter Grünberg Institut, Rheinisch-Westfälische Technische Hochschule Aachen University (RWTH), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), RIKEN Center for Emergent Matter Science (CEMS) (CEMS), RIKEN - Institute of Physical and Chemical Research [Japon] (RIKEN), Department of Physics [Budapest], Budapest University of Technology and Economics [Budapest] (BME), and Peter Grünberg Institut (PGI)

Subjects
ddc:530, Condensed Matter::Strongly Correlated Electrons, [PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], ddc:620, ComputingMilieux_MISCELLANEOUS
Abstract

The Dzyaloshinskii–Moriya interaction (DMI), i.e., the antisymmetric part of the exchange coupling tensor, favors the perpendicular arrangement of magnetic moment, thus inducing canting in otherwise collinear structures. The DMI is the prerequisite for the emergence of weak ferromagnetism in antiferromagnets, but can stabilize twisted magnetic textures, such as spin spirals, soliton lattices, and magnetic skyrmions. While the magnitude of the DMI determines the canting angle of adjacent spins, its sign dictates the sense of the spin rotation. Based on focused polarized neutron diffraction (PND) study, combined with symmetry analysis, we determine the sign of the DMI in the unconventional multiferroic Ba 2 CoGe 2 O 7 and reveal its detailed magnetic structure in magnetic fields applied in the tetragonal plane. As PND gives unique access to the scattering contribution from the phase-sensitive nuclear-magnetic interference, it is a valuable tool for a straightforward DMI sign determination in bulk materials and allows to disclose even very weak magnetic moments. Remarkably, the sign of the DMI could be determined from the PND measurement of a single reflection, which is demonstrated to be reliable for a large range of applied magnetic field directions and values.

Published
2022

16. Magnetic anisotropies of Ho(III) and Dy(III) single-molecule magnets experimentally determined via polarized neutron diffraction

Author

Klahn, Emil Andreasen, Thiel, Andreas Munch, Degn, Rasmus B., Kibalin, Iurii, Gukasov, Arsen, wilson, claire, Canaj, Angelos B., Murrie, Mark, and Overgaard, Jacob

Abstract

We present the magnetic anisotropy of two isostructural pentagonal-bipyramidal complexes, [Ln(H2O)5(HMPA)2]I3.2HMPA (HMPA=hexamethylphosphoramide, Ln=Dy, Ho). Using ac magnetic susceptibility measurements, we find magnetic relaxation barriers of 600 K and 270 K for the Dy- and Ho-compounds, respectively. This difference is supported by polarized neutron diffraction (PND) measured at 5 K and 1 T which provides the first experimental evidence that the transverse elements in the magnetic anisotropy of the Ho-analogue are significant, whereas the Dy-analogue has a near-axial magnetic anisotropy with vanishing transverse contributions. The coordination geometries of the two complexes are highly similar, and we attribute the loss of strong magnetic axiality as expressed in the atomic susceptibility tensors from PND, as well as the smaller relaxation barrier in the Ho-complex compared to the Dy-complex, to the less favorable interaction of the pentagonal bipyramidal crystal field with the characteristics of the Ho(III) 4f-charge distribution.

Published
2021

21. Magnetization Density Distribution of Sr2IrO4: Deviation from a Local jeff=1/2 Picture

Author

Jeong, Jaehong, Lenz, Benjamin, Gukasov, Arsen, Fabrèges, Xavier, Sazonov, Andrew, Hutanu, Vladimir, Louat, Alex, Bounoua, Dalila, Martins, Cyril, Biermann, Silke, Brouet, Véronique, Sidis, Yvan, Bourges, Philippe, Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre de Physique Théorique [Palaiseau] (CPHT), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Institut de minéralogie et de physique des milieux condensés (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut für Textiltechnik der RWTH [Aachen] (ITA), Rheinisch-Westfälische Technische Hochschule Aachen (RWTH), Laboratoire de Physique des Solides (LPS), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Systèmes étendus et magnétisme (LCPQ) (SEM), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Collège de France (CdF (institution)), European Theoretical Spectroscopy Facility, LLB - Nouvelles frontières dans les matériaux quantiques (NFMQ), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Rheinisch-Westfälische Technische Hochschule Aachen University (RWTH), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
[PHYS]Physics [physics], Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), FOS: Physical sciences, [PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], ComputingMilieux_MISCELLANEOUS
Abstract

$5d$ iridium oxides are of huge interest due to the potential for new quantum states driven by strong spin-orbit coupling. The strontium iridate Sr$_2$IrO$_4$ is particularly in the spotlight because of the so-called $j_\text{eff}=1/2$ state consisting of a quantum superposition of the three local $t_{2g}$ orbitals with -- in its most simple version -- nearly equal population, which stabilizes an unconventional Mott insulating state. Here, we report an anisotropic and aspherical magnetization density distribution measured by polarized neutron diffraction in a magnetic field up to 5~T at 4~K, which strongly deviates from a local \jeffHalf picture even when distortion-induced deviations from the equal weights of the orbital populations are taken into account. Once reconstructed by the maximum entropy method and multipole expansion model refinement, the magnetization density shows cross-shaped positive four lobes along the crystallographic tetragonal axes with a large spatial extent, showing that the $xy$ orbital contribution is dominant. The analogy to the superconducting copper oxide systems might then be weaker than commonly thought., Comment: 3 figures + supplementary file included

Published
2020

28. Magnetization Density Distribution ofSr2IrO4: Deviation from a Localjeff=1/2Picture

Author

Jeong, Jaehong, primary, Lenz, Benjamin, additional, Gukasov, Arsen, additional, Fabrèges, Xavier, additional, Sazonov, Andrew, additional, Hutanu, Vladimir, additional, Louat, Alex, additional, Bounoua, Dalila, additional, Martins, Cyril, additional, Biermann, Silke, additional, Brouet, Véronique, additional, Sidis, Yvan, additional, and Bourges, Philippe, additional

Published
2020
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29. Magnetic Order and Sign of the Dzyaloshinskii–Moriya Interaction in 2-D Antiferromagnet Ba 2 CoGe 2 O 7 Under Applied Magnetic Field.

Author

Thoma, Henrik, Hutanu, Vladimir, Dutta, Rajesh, Gukasov, Arsen, Kocsis, Vilmos, Tokunaga, Yusuke, Taguchi, Yasujiro, Tokura, Yoshinori, Kezsmarki, Istvan, Roth, Georg, and Angst, Manuel

Subjects
MAGNETIC fields, MAGNETIC structure, MAGNETIC moments, NEUTRON diffraction, PERPENDICULAR magnetic anisotropy
Abstract

The Dzyaloshinskii–Moriya interaction (DMI), i.e., the antisymmetric part of the exchange coupling tensor, favors the perpendicular arrangement of magnetic moment, thus inducing canting in otherwise collinear structures. The DMI is the prerequisite for the emergence of weak ferromagnetism in antiferromagnets, but can stabilize twisted magnetic textures, such as spin spirals, soliton lattices, and magnetic skyrmions. While the magnitude of the DMI determines the canting angle of adjacent spins, its sign dictates the sense of the spin rotation. Based on focused polarized neutron diffraction (PND) study, combined with symmetry analysis, we determine the sign of the DMI in the unconventional multiferroic Ba2CoGe2O7 and reveal its detailed magnetic structure in magnetic fields applied in the tetragonal plane. As PND gives unique access to the scattering contribution from the phase-sensitive nuclear-magnetic interference, it is a valuable tool for a straightforward DMI sign determination in bulk materials and allows to disclose even very weak magnetic moments. Remarkably, the sign of the DMI could be determined from the PND measurement of a single reflection, which is demonstrated to be reliable for a large range of applied magnetic field directions and values. [ABSTRACT FROM AUTHOR]

Published
2022
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30. Spin resolved electron density study of YTiO 3 in its ferromagnetic phase: signature of orbital ordering

Author

Voufack, Ariste, Kibalin, Iurii, Yan, Zeyin, Claiser, Nicolas, Gueddida, Saber, Gillon, Béatrice, Porcher, Florence, Gukasov, Arsen, Sugimoto, Kunishisa, Lecomte, Claude, Dahaoui, Slimane, Gillet, Jean-Michel, Souhassou, Mohamed, Cristallographie, Résonance Magnétique et Modélisations (CRM2), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), PNIP NRC, Kurcharov Institut, Laboratoire Structures, Propriétés et Modélisation des solides (SPMS), Institut de Chimie du CNRS (INC)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Japan Synchrotron Radiation Research Institute [Hyogo] (JASRI), Laboratoire de Physique et Chimie Théoriques (LPCT), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
computational modelling, perovskites, inorganic materials, magnetic order, multipolar refinement, X-ray diffraction, polarized neutron diffraction, charge density, spin density, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], orbital ordering, YTiO 3, materials modelling, properties of solids
Abstract

International audience; The present work reports on the charge and spin density modelling of YTiO 3 in its ferromagnetic state (T C = 27 K). Accurate polarized neutron diffraction and high-resolution X-ray diffraction (XRD) experiments were carried out on a single crystal at the ORPHÉ E reactor (LLB) and SPRING8 synchrotron source. The experimental data are modelled by the spin resolved pseudo-atomic multipolar model (Deutsch et al., 2012). The refinement strategy is discussed and the result of this electron density modelling is compared with that from XRD measured at 100 K and with density functional theory calculations. The results show that the spin and charge densities around the Ti atom have lobes directed away from the O atoms, confirming the filling of the t 2g orbitals of the Ti atom. The d xy orbital is less populated than d xz and d yz , which is a sign of a partial lift of degeneracy of the t 2g orbitals. This study confirms the orbital ordering at low temperature (20 K), which is already present in the paramagnetic state above the ferromagnetic transition (100 K).

Published
2019

31. Spin resolved electron density study of YTiO3 in its ferromagnetic phase: signature of orbital ordering

Author

Voufack, Ariste Bolivard, primary, Kibalin, Iurii, additional, Yan, Zeyin, additional, Claiser, Nicolas, additional, Gueddida, Saber, additional, Gillon, Béatrice, additional, Porcher, Florence, additional, Gukasov, Arsen, additional, Sugimoto, Kunishisa, additional, Lecomte, Claude, additional, Dahaoui, Slimane, additional, Gillet, Jean-Michel, additional, and Souhassou, Mohamed, additional

Published
2019
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32. Neutron diffraction study of magnetism in van der Waals layered MnBi2nTe3n+1.

Author

Ding, Lei, Hu, Chaowei, Feng, Erxi, Jiang, Chenyang, Kibalin, Iurii A, Gukasov, Arsen, Chi, MiaoFang, Ni, Ni, and Cao, Huibo

Subjects
QUANTUM Hall effect, MAGNETISM, MAGNETIC structure, MAGNETIC materials, MAGNETIC crystals, ANOMALOUS Hall effect, NEUTRON diffraction
Abstract

Two-dimensional van der Waals MnBi2nTe3n+1 (n = 1, 2, 3, 4) compounds have been recently found to be intrinsic magnetic topological insulators rendering quantum anomalous Hall effect and diverse topological states. Here, we summarize and compare the crystal and magnetic structures of this family, and discuss the effects of chemical composition on their magnetism. We found that a considerable fraction of Bi occupies at the Mn sites in MnBi2nTe3n+1 (n = 1, 2, 3, 4) while there is no detectable Mn at the non-magnetic atomic sites within the resolution of neutron diffraction experiments. The occupancy of Mn monotonically decreases with the increase of n. The polarized neutron diffraction on the representative MnBi4Te7 reveals that its magnetization density is exclusively accumulated at the Mn site, in good agreement with the results from the unpolarized neutron diffraction. The defects of Bi at the Mn site naturally explain the continuously reduced saturated magnetic moments from n = 1 to n = 4. The experimentally estimated critical exponents of all the compounds generally suggest a three-dimensional character of magnetism. Our work provides material-specified structural parameters that may be useful for band structure calculations to understand the observed topological surface states and for designing quantum magnetic materials through chemical doping. [ABSTRACT FROM AUTHOR]

Published
2021
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33. Spin‐resolved atomic orbital model refinement for combined charge and spin density analysis: application to the YTiO3 perovskite.

Author

Kibalin, Iurii, Voufack, Ariste Bolivard, Souhassou, Mohamed, Gillon, Béatrice, Gillet, Jean-Michel, Claiser, Nicolas, Gukasov, Arsen, Porcher, Florence, and Lecomte, Claude

Subjects
ATOMIC orbitals, ATOMIC models, PEROVSKITE, NUCLEAR magnetic resonance, NEUTRON diffraction, DENSITY
Abstract

A new crystallographic method is proposed in order to refine a spin‐resolved atomic orbital model against X‐ray and polarized neutron diffraction data. This atomic orbital model is applied to the YTiO3 perovskite crystal, where orbital ordering has previously been observed by several techniques: X‐ray diffraction, polarized neutron diffraction and nuclear magnetic resonance. This method gives the radial extension, orientation and population of outer atomic orbitals for each atom. The interaction term between Ti3+, Y3+ cations and O2− ligands has been estimated. The refinement statistics obtained by means of the orbital method are compared with those obtained by the multipole model previously published. [ABSTRACT FROM AUTHOR]

Published
2021
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34. Structural and magnetic phase transitions in Cs-2[FeCl5(H2O)]

Author

Froehlich, Tobias, Stein, Jonas, Bohaty, Ladislav, Becker, Petra, Gukasov, Arsen, Braden, Markus, Froehlich, Tobias, Stein, Jonas, Bohaty, Ladislav, Becker, Petra, Gukasov, Arsen, and Braden, Markus

Abstract

The compound Cs-2[FeCl5(H2O)] is magnetoelectric but not multiferroic with an erythrosiderite-related structure. We present a comprehensive investigation of its structural and antiferromagnetic phase transitions by polarization microscopy, pyroelectric measurements, x-ray diffraction and neutron diffraction. At about (157.6 +/- 0.1) K, the compound changes its symmetry from Cmcm to I2/c, with a doubling of the original c-axis. This transformation is associated with rotations of the [FeCl5O] octahedra and corresponds to an ordering of the H2O molecules and of the related H bonds. A significant ferroelectric polarization can be excluded for this transition by precise pyrocurrent measurements. The antiferromagnetic phase transition occurring at 6.4K results in the magnetic space group I2'/c, which perfectly agrees with previous measurements of the linear magnetoelectric effect and magnetization.

Published
2018

41. Exploring metamagnetism of single crystalline EuNiGe$_3$ by neutron scattering

Author

Fabrèges, Xavier, Gukasov, Arsen, Bonville, Pierre, Maurya, A, Thamizhavel, A, Dhar, S, Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Laboratoire Nano-Magnétisme et Oxydes (LNO), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Department of Condensed Matter Physics and Materials Science [TIFR] (CMPMS), Tata Institute for Fundamental Research (TIFR), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], mean field theory, Neutron scattering, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], metamagnetism
Abstract

International audience; We present here a neutron diffraction study, both in zero field and as a function of magnetic field, of the magnetic structure of the tetragonal intermetallic EuNiGe$_3$ on a single crystalline sample. This material is known to undergo a cascade of transitions, first at 13.2 K towards an incommensurate modulated magnetic structure, then at 10.5 K to an antiferromagnetic structure. We show here that the low-temperature phase presents a spiral moment arrangement with wave vector $k$ = ($1\over 4$ ,δ,0). For a magnetic field applied along the tetragonal $c$ axis, the square root of the scattering intensity of the (1 0 1) reflection matches very well the complex metamagnetic behavior of the magnetization along $c$ measured previously. For the magnetic field applied along the $b$ axis, two magnetic transitions are observed below the transition to a fully polarized state.

Published
2016

44. Spin, charge and momentum densities of YTiO3 perovskyte

Author

Souhassou, Mohamed, primary, Bolivard, Voufack, additional, Claiser, Nicolas, additional, Deutsch, Maxime, additional, Lacomte, Claude, additional, Gillet, Jean Michel, additional, Cortona, Pietro, additional, Yan, Zeyin, additional, Kibalin, Iurii, additional, Gillon, Béatrice, additional, Porcher, Florence, additional, Gukasov, Arsen, additional, Sakurai, Yoshiharu, additional, Itou, Masayoshi, additional, and Itoh, Masahisa, additional

Published
2016
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45. Probability densities in different spaces: when multipolar-atom model is just not enough

Author

Gillet, Jean-Michel, primary, Yan, Zeyin, additional, Kibalin, Iurii, additional, Voufack, Bolivard, additional, Claiser, Nicolas, additional, Deutsch, Maxime, additional, Gillon, Beatrice, additional, Lecomte, Claude, additional, Cortona, Pietro, additional, Genoni, Alessandro, additional, Sakurai, Yoshiharu, additional, Itou, Masayoshi, additional, Itoh, Masahisa, additional, Brancewicz, Marek, additional, Tsuji, Naruki, additional, Gukasov, Arsen, additional, Porcher, Florence, additional, and Souhassou, Mohamed, additional

Published
2016
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47. Origin of the large dispersion of magnetic properties in nanostructured oxides : FexO/Fe3O4 nanoparticles as a case study

Author

Estrader, Marta, Lopez-Ortega, Alberto, Golosovsky, Igor V., Estrade, Sonia, Roca, Alejandro G., Salazar-Alvarez, German, Lopez-Conesa, Lluis, Tobia, Dina, Winkler, Elin, Ardisson, Jose D., Macedo, Waldemar A. A., Morphis, Andreas, Vasilakaki, Marianna, Trohidou, Kalliopi N., Gukasov, Arsen, Mirebeau, Isabelle, Makarova, O. L., Zysler, Roberto D., Peiro, Francesca, Baro, Maria Dolors, Bergström, Lennart, Nogues, Josep, Estrader, Marta, Lopez-Ortega, Alberto, Golosovsky, Igor V., Estrade, Sonia, Roca, Alejandro G., Salazar-Alvarez, German, Lopez-Conesa, Lluis, Tobia, Dina, Winkler, Elin, Ardisson, Jose D., Macedo, Waldemar A. A., Morphis, Andreas, Vasilakaki, Marianna, Trohidou, Kalliopi N., Gukasov, Arsen, Mirebeau, Isabelle, Makarova, O. L., Zysler, Roberto D., Peiro, Francesca, Baro, Maria Dolors, Bergström, Lennart, and Nogues, Josep

Abstract

The intimate relationship between stoichiometry and physicochemical properties in transition-metal oxides makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between the magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxides., AuthorCount:22

Published
2015
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48. Polarized Neutron Diffraction as a Tool for Mapping Molecular Magnetic Anisotropy: Local Susceptibility Tensors in CoII Complexes

Author

Ridier, Karl, primary, Gillon, Béatrice, additional, Gukasov, Arsen, additional, Chaboussant, Grégory, additional, Cousson, Alain, additional, Luneau, Dominique, additional, Borta, Ana, additional, Jacquot, Jean-François, additional, Checa, Ruben, additional, Chiba, Yukako, additional, Sakiyama, Hiroshi, additional, and Mikuriya, Masahiro, additional

Published
2015
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49. Source of magnetic anisotropy in quasi-two-dimensional XY $\{ Cu_4(tetrenH_5)W(CN)_8]_4 ⋅7.2 H_{2}O)\}_n$ bilayer molecular magnet

Author

Zaharko, Oksana, Pregelj, M., Zorko, A., Podgajny, Robert, Gukasov, Arsen, Van Tol, Johan, Klokishner, Sophia, Ostrovsky, S., and Delley, Bernard

Abstract

To identify the origin of the XY spin dimensionality in the bilayered system {Cu4(tetrenH5)[W(CN)8]4⋅7.2H2O}n (WCuT) we use a combination of single-crystal experiments (bulk magnetization, neutron flipping ratio, electron magnetic resonance, neutron diffraction) and theoretical modeling (exchange-charge model of the crystal field, dipolar energy, and density functional calculations). Our experiments show that the magnetic properties of WCuT are anisotropic and two-dimensional correlations build up below 70 K. The hard anisotropy axis is perpendicular to the layers (b axis) and a small anisotropy within the ac layers is present. Modeling of the crystal field validates treatment of tungsten and copper as spin S=12 ions with anisotropic g values. The local magnetic anisotropy results from the common action of the crystal field and spin-orbit coupling and is along the c axis for both ions. Density functional calculations identify the origin of the ferromagnetic exchange in different energies and symmetries of the tungsten- and copper-dominated orbitals and anticipate different exchange couplings across the apical (along the b axis) and equatorial (in the ac plane) Cu-CN-W bridges due to difference in the hybridization efficiency. Calculation of the dipolar energy for various spin configurations suggests that dipolar interactions play a decisive role in the ac-planar anisotropy in this system. We propose that the effective XY spin dimensionality in WCuT is established by a combination of the axial local anisotropy of the W and Cu ions and the long-range magnetic dipolar interactions on the bilayered square lattice.

Published
2013

50. H‐Mediated Magnetic Interactions between Layers in a 2D MnII–Dicyanamide Polymer: Neutron Diffraction, DFT, and Quantum Monte Carlo Calculations.

Author

Gillon, Béatrice, Hammerschmied, Albert, Gukasov, Arsen, Cousson, Alain, Cauchy, Thomas, Ruiz, Eliseo, Schlueter, John A., and Manson, Jamie L.

Subjects
NEUTRON diffraction, ELECTROMAGNETIC interactions, QUANTUM Monte Carlo method, DENSITY functional theory, COUPLING reactions (Chemistry)
Abstract

We report neutron‐diffraction investigations of the quasi‐2D MnII(dca)2(pym)(H2O) (pym = N2C4H4) compound, where high‐spin MnII ions are bridged by dicyanamide anions, [N(CN)2]– (herein abbreviated dca). Inside the layers, Mn2+ ions are connected by single or double dca bridges. The magnetic phase diagram was established by neutron diffraction on a single crystal. In the low‐field phase, the MnII ions are antiferromagnetically ordered in the layers, with moments nearly parallel to the c axis, and the layers are antiferromagnetically coupled. The spin‐flop phase corresponds to ferromagnetic coupling between the antiferromagnetic layers, in which the MnII moments are nearly perpendicular to the c axis. The induced spin‐density distribution in the paramagnetic phase, determined by polarized neutron diffraction, visualizes the superexchange pathways through the dca ligands within the layers and through H bonding between neighboring layers. The theoretical spin density obtained by bidimensional periodic DFT calculations is compared with the experimental results. Furthermore, quantum Monte Carlo simulations have been performed to compare the DFT results with experimental susceptibility measurements. [ABSTRACT FROM AUTHOR]

Published
2018
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