Author
Hidehisa Ohta
Bio: Hidehisa Ohta is an academic researcher from University of Tsukuba. The author has contributed to research in topics: Physics & Density functional theory. The author has an hindex of 1, co-authored 2 publications receiving 2 citations.
Papers
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TL;DR: In this paper, the spin density functional theory was used to calculate the orbital magnetic moments in uranium monochalcogenides, where X =S, Se, and Te.
Abstract: We study the orbital, spin, and total magnetic moments in uranium monochalcogenides, U X where X =S, Se, and Te, using the fully relativistic full-potential calculations based on the spin density functional theory. In particular, the orbital magnetic moments are calculated with the Dirac current. We employ two methods which adopt distinctly different basis sets; one is the fully relativistic full-potential linear-combination-of-atomic-orbitals (FFLCAO) method and the other is the fully relativistic full-potential mixed-basis (FFMB) method. Showing that the orbital magnetic moments calculated using the FFLCAO method and those calculated using the FFMB method agree very well with each other, we demonstrate that, in contrast to the conventional method, the method with the Dirac current enables us to calculate the orbital magnetic moments even if the basis set includes basis functions with no definite angular momenta, e.g., the plane waves in the FFMB method. Furthermore, it is found that the orbital magnetic...
3 citations
TL;DR: Fujihala et al. as discussed by the authors reported the magnetic structure and anisotropy of the quasi-one-dimensional antiferromagnet (S=\frac{1}{2}$ ) obtained by single-crystal neutron scattering, electron spin resonance (ESR), and magnetization measurements, following an earlier study of its dynamics.
Abstract: We report the magnetic structure and anisotropy of the quasi-one-dimensional $S=\frac{1}{2}$ antiferromagnet ${\mathrm{Na}}_{2}{\mathrm{CuSO}}_{4}{\mathrm{Cl}}_{2}$ obtained by single-crystal neutron scattering, electron spin resonance (ESR), and magnetization measurements, following an earlier study of its dynamics [M. Fujihala et al., Phys. Rev. B 101, 024410 (2020)]. A N\'eel-type spin structure is formed within the chain of this compound, where the spins point along the $b$ axis, and ESR data indicate an antisymmetric exchange with a uniform Dzyaloshinskii-Moriya (DM) vector pointing along the $b$ axis. The anisotropy $g$ factor and magnetic structure are strong indicators of magnetic anisotropy originating from a symmetric anisotropic exchange interaction and/or a magnetic dipole interaction. These results suggest that these terms of the anisotropic spin Hamiltonian counteract the effect of the DM interaction and stabilize the N\'eel-type structure in ${\mathrm{Na}}_{2}{\mathrm{CuSO}}_{4}{\mathrm{Cl}}_{2}$.
2 citations
TL;DR: In this article, the dependence of the structural properties of uranium monochalcogenides, U X where X = S, Se, and Te, as well as their electronic ones on the exchange-correlation energy functionals within the spin density functional theory, carrying out all electron calculations by the fully relativistic full-potential linear-combination-of-atomic-orbitals method.
Abstract: We study the dependence of the structural properties of uranium monochalcogenides, U X where X = S, Se, and Te, as well as their electronic ones on the exchange–correlation energy functionals within the spin density functional theory, carrying out all electron calculations by the fully relativistic full-potential linear-combination-of-atomic-orbitals method. We employ two functionals of the local spin density approximation (LSDA) and two functionals of the generalized gradient approximations (GGA); the former two are the Perdew–Zunger and Perdew–Wang functionals and the latter two are the Perdew–Burke–Ernzerhof (PBE) and PBEsol functionals. We also examine the effects of the relativistic correction to the LSDA exchange part of each functional. We find that, for lattice constants, bulk moduli, and cohesive energies, the results of the calculations using the PBE functional are in the best agreement with the experimental results. On the contrary, we find that calculated total magnetic moments and one-electro...
1 citations
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TL;DR: An all-electron DKS approach based on the use of G-spinor basis sets, Hermite Gaussian functions, state-of-the-art density-fitting techniques and memory distributed parallelism is described, which would make possible to describe molecules in strong fields, accurately accounting for relativistic kinematic effects and spin-orbit coupling.
Abstract: We review recent theoretical and computational advances in the full relativistic four-component Dirac–Kohn–Sham (DKS) approach and its application to the calculation of the electronic structure of chemical systems containing many heavy atoms. We describe our implementation of an all-electron DKS approach based on the use of G-spinor basis sets, Hermite Gaussian functions, state-of-the-art density-fitting techniques and memory distributed parallelism. This approach has enormously extended the applicability of the DKS method, including for example large clusters of heavy atoms, and opens the way for future key developments. We examine the current limitations and future possible applications of the DKS approach, including the implementation of four-current density functionals and real-time propagation schemes. This would make possible to describe molecules in strong fields, accurately accounting for relativistic kinematic effects and spin–orbit coupling.
62 citations
TL;DR: In this article, the dependence of the structural properties of uranium monochalcogenides, U X where X = S, Se, and Te, as well as their electronic ones on the exchange-correlation energy functionals within the spin density functional theory, carrying out all electron calculations by the fully relativistic full-potential linear-combination-of-atomic-orbitals method.
Abstract: We study the dependence of the structural properties of uranium monochalcogenides, U X where X = S, Se, and Te, as well as their electronic ones on the exchange–correlation energy functionals within the spin density functional theory, carrying out all electron calculations by the fully relativistic full-potential linear-combination-of-atomic-orbitals method. We employ two functionals of the local spin density approximation (LSDA) and two functionals of the generalized gradient approximations (GGA); the former two are the Perdew–Zunger and Perdew–Wang functionals and the latter two are the Perdew–Burke–Ernzerhof (PBE) and PBEsol functionals. We also examine the effects of the relativistic correction to the LSDA exchange part of each functional. We find that, for lattice constants, bulk moduli, and cohesive energies, the results of the calculations using the PBE functional are in the best agreement with the experimental results. On the contrary, we find that calculated total magnetic moments and one-electro...
1 citations
TL;DR: In this paper , the importance of the Dzyaloshinskii-Moriya interaction (DMI) to the magnetic properties of quantum spin systems is discussed mainly focusing on the determination of or understanding the role of DMI extracted from high-frequency high-field electron spin resonance (ESR) measurements.
Abstract: In this review, the importance of the Dzyaloshinskii–Moriya Interaction (DMI) to the magnetic properties of quantum spin systems is discussed mainly focusing on the determination of or understanding the role of DMI extracted from high-frequency high-field electron spin resonance (ESR) measurements. This review includes the ESR theories of the S = 1/2 one-dimensional (1D) antiferromagnet with the staggered field (Oshikawa–Affleck theory) and with the uniform DMI, and several related experimental results are shown. Then, the proposed mechanisms of the singlet–triplet transition in quantum spin systems together with the ESR selection rules are introduced in connection with various experimental results. Finally, the role of DMI in the ground state of kagome lattice antiferromagnets and the honeycomb lattice antiferromagnet is discussed with some experimental results.
TL;DR: In this article , the magnetic properties of uranium monochalcogenides, UQ (Q = S, Se, and Te), were investigated by applying relativistic full potential density functional theory with the generalized gradient approximation (GGA), GGA+U, and GGA + OP (orbital polarization) methods, by calculating X-ray magnetic circular dichroism (XMCD) spectra of U in UQ systems at the U M45, N45, and L23 edges.
Abstract: In this study, by applying relativistic full potential density functional theory with the generalized gradient approximation (GGA), GGA + U, and GGA + OP (orbital polarization) methods, we have investigated the magnetic properties of uranium monochalcogenides, UQ (Q = S, Se, and Te). The emphasis here is to calculate X-ray magnetic circular dichroism (XMCD) spectra of U in UQ systems at the U M45, N45, and L23 edges and compare the spectra as well as deduced parameters such as spin, orbital, and total magnetic moments with the available experimental and computational results. The effect of the Hubbard (U) parameter on the 5f electrons of uranium is also scrutinized to probe the electron correlation effects in UQ for their electronic and magnetic properties. The spin and orbital sum rule analyses have been carried out on the computed U M45 and N45 XMCD spectra. The corresponding spin, orbital, and total magnetic moments and the ratio of orbital and spin magnetic moments determined for UQ systems are found to be in good agreement with experiments when we use the GGA + OP method.
TL;DR: In this article , high-field electron spin resonance spectroscopy and magnetization studies of Ca 3 ReO 5 Cl 2 , allowing us not only to refine spin-Hamiltonian parameters, but also to investigate peculiarities of its low-energy spin dynamics.
Abstract: Abstract The observation of spinon excitations in the $$S=\frac{1}{2}$$ S = 1 2 triangular antiferromagnet Ca 3 ReO 5 Cl 2 reveals a quasi-one-dimensional (1D) nature of magnetic correlations, in spite of the nominally 2D magnetic structure. This phenomenon is known as frustration-induced dimensional reduction. Here, we present high-field electron spin resonance spectroscopy and magnetization studies of Ca 3 ReO 5 Cl 2 , allowing us not only to refine spin-Hamiltonian parameters, but also to investigate peculiarities of its low-energy spin dynamics. We argue that the presence of the uniform Dzyaloshinskii-Moriya interaction (DMI) shifts the spinon continuum in momentum space and, as a result, opens a zero-field gap at the Γ point. We observed this gap directly. The shift is found to be consistent with the structural modulation in the ordered state, suggesting this material as a perfect model triangular-lattice system, where a pure DMI-spiral ground state can be realized.