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Journal Articles

Spin torques and electrical voltage generation in antiferromagnetic nanotextures

Yamane, Yuta*; Ieda, Junichi

Magune, 13(5), p.235 - 241, 2018/10

Journal Articles

Magnetic anisotropy by Rashba spin-orbit coupling in antiferromagnetic thin films

Ieda, Junichi; Barnes, S. E.*; Maekawa, Sadamichi

Journal of the Physical Society of Japan, 87(5), p.053703_1 - 053703_4, 2018/05

 Times Cited Count:2 Percentile:76.74(Physics, Multidisciplinary)

Journal Articles

Structure of the magnetic excitations in the spin-1/2 triangular-lattice Heisenberg antiferromagnet Ba$$_{3}$$CoSb$$_{2}$$O$$_{9}$$

Ito, Saya*; Kurita, Nubuyuki*; Tanaka, Hidekazu*; Kawamura, Seiko; Nakajima, Kenji; Ito, Shinichi*; Kuwahara, Keitaro*; Kakurai, Kazuhisa*

Nature Communications (Internet), 8, p.235_1 - 235_6, 2017/08

 Times Cited Count:31 Percentile:5.9(Multidisciplinary Sciences)

Journal Articles

Spin-transfer torques in antiferromagnetic textures; Efficiency and quantification method

Yamane, Yuta*; Ieda, Junichi; Sinova, J.*

Physical Review B, 94(5), p.054409_1 - 054409_8, 2016/08

AA2016-0164.pdf:0.5MB

 Times Cited Count:16 Percentile:25.16(Materials Science, Multidisciplinary)

We formulate a theory of spin-transfer torques in antiferromagnets, which covers the small to large limits of the exchange coupling energy relative to the kinetic energy of the inter-sublattice electron dynamics. Our theory suggests a natural definition of the efficiency of spin-transfer torques in antiferromagnets in terms of well-defined material parameters, revealing that the charge current couples predominantly to the antiferromagnetic order parameter and the sublattice-canting moment in, respectively, the limits of large and small exchange coupling. The effects can be quantified by analyzing the antiferromagnetic spin-wave dispersions in the presence of charge current: in the limit of large exchange coupling the spin-wave Doppler shift always occurs, whereas, in the opposite limit, the only spin-wave modes to react to the charge current are ones that carry a pronounced sublattice-canting moment. The findings offer a framework for understanding and designing spin-transfer torques in antiferromagnets belonging to different classes of sublattice structures such as, e.g., bipartite and layered antiferromagnets.

Journal Articles

Incommensurate to commensurate antiferromagnetism in CeRhAl$$_4$$Si$$_2$$; An $$^{27}$$Al NMR study

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Ghimire, N. J.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*

Physical Review B, 93(1), p.014402_1 - 014402_9, 2016/01

 Times Cited Count:1 Percentile:91.65(Materials Science, Multidisciplinary)

$$^{27}$$Al nuclear magnetic resonance (NMR) experiments have been performed on a single crystal of CeRhAl$$_4$$Si$$_2$$, which is an antiferromagnetic Kondo-lattice compound with successive antiferromagnetic transitions of $$T_{rm N1}$$=14 K and $$T_{rm N2}$$=9 K at zero external field. In the paramagnetic state, the Knight shifts, quadrupolar frequency, and asymmetric parameter of electrical field gradient on the Al sites have been determined, which have local orthorhombic symmetry. The transferred hyperfine coupling constants are also determined. Analysis of the NMR spectra indicates that a commensurate antiferromagnetic structure exists below $$T_{rm N2}$$, but an incommensurate modulation of antiferromagnetic moments is present in the antiferromagnetic state between $$T_{rm N1}$$ and $$T_{rm N2}$$. The spin-lattice relaxation rate suggests that the $$4f$$ electrons behave as local moments at temperatures above $$T_{rm N1}$$.

Journal Articles

Exotic field induced quantum phase transition of the kagome lattice antiferromagnet

Sakai, Toru; Nakano, Hiroki*

Physics Procedia, 75, p.821 - 828, 2015/12

 Times Cited Count:0 Percentile:100

The magnetization process of the S=1/2 kagome-lattice antiferromagnet is investigated using the numerical diagonalization up to 42-spin clusters. The critical exponent analysis confirms the unconventional magnetization behavior around the 1/3 magnetization plateau-like anomaly; the field derivative is infinite at the low-field side, while it is zero at the high-field side. We also confirm that a magnetization jump appears at 1/3 of the saturation magnetization in distorted kagome-lattice antiferromagnets.

Journal Articles

Instability of a ferrimagnetic state of a frustrated S=1/2 Heisenberg antiferromagnet in two dimensions

Nakano, Hiroki*; Sakai, Toru

Japanese Journal of Applied Physics, 54(3), p.030305_1 - 030305_4, 2015/03

 Times Cited Count:9 Percentile:49.81(Physics, Applied)

To clarify the instability of the ferrimagnetism which is the fundamental magnetism of ferrite, numerical-diagonalization study is carried out for the two-dimensional S=1/2 Heisenberg antiferromagnet with frustration. We find that the ferrimagnetic ground state has the spontaneous magnetization in small frustration.

Journal Articles

Magnetization plateaux of the ${it S}$=1/2 two-dimensional frustrated antiferromagnet Cs$$_{2}$$CuBr$$_{4}$$

Ono, Toshio*; Tanaka, Hidekazu*; Kolomiyets, O.*; Mitamura, Hiroyuki*; Goto, Tsuneaki*; Nakajima, Kenji; Osawa, Akira; Koike, Yoshihiro; Kakurai, Kazuhisa; Klenke, J.*; et al.

Journal of Physics; Condensed Matter, 16(11), p.S773 - S778, 2004/03

 Times Cited Count:56 Percentile:10.79(Physics, Condensed Matter)

no abstracts in English

JAEA Reports

A study on properties of uranium oxide using band theory

Tejima, Shogo

JNC-TN8400 2000-029, 54 Pages, 2000/10

JNC-TN8400-2000-029.pdf:1.32MB

This report describes the study done by the author as a postdoctoral research associate at Japan Nuclear Cycle Development Institute. This report is divided into three parts: construction of a relativistic band calculation formalism based on the density functional theory, using this method, investigation of the electrical properties for ferromagnetic UGe$$_{2}$$ and antiferromagnetic UO$$_{2}$$. (1)A relativistic band calculation (RBC) method. Band calculations for the s, p, and d electric structure have been developed well in the practical application and theoretical study. But band calculation method treating magnetic 5f electrons as actinide compounds are complicated and needed relativistic approach, so it is behind with the study of the 5f system. In this study we construct the relativistic band calculationformalism valid for magnetic 5f electrons. (2)Electric properties of UGe$$_{2}$$. The actinide compounds UGe$$_{2}$$ is ferromagnetic, so the theoretical analysis is not well yet. The electric structure and fermi surface of UGe$$_{2}$$ are analyzed using the RBC. The theoretical results show that UGe$$_{2}$$ is heavy electron with the 5f character and are agreement with experimental one. (3)Electric structure of nuclear fuel UO$$_{2}$$. It is important to understand the mechanism of the thermal conductivity of nuclear fuel as antiferromagnetic UO$$_{2}$$. The UO$$_{2}$$ band calculation reflecting the thermal properties, into account of relativistic effect, have not done yes. So using the RBC the detailed electric structure of UO$$_{2}$$ are obtained.

Journal Articles

$$^{235}$$U NMR study of antiferromagnet UO$$_{2}$$

Ikushima, Kenji; Yasuoka, Hiroshi; Tsutsui, Satoshi; Nasu, Saburo*; Masaki, Nobuyuki; Nakamura, Akio; Ueda, Yutaka*

Physica B; Condensed Matter, 281-282, p.197 - 199, 2000/06

 Times Cited Count:2 Percentile:83.51

no abstracts in English

Journal Articles

Magnetic and neutron diffraction study on perovskites La$$_{1-x}$$Sr$$_{x}$$CrO$$_{3}$$

*; Hinatsu, Yukio*; Nakamura, Akio; Inami, Toshiya; Shimojo, Yutaka; Morii, Yukio

Journal of Solid State Chemistry, 141, p.404 - 410, 1998/00

 Times Cited Count:79 Percentile:4.23(Chemistry, Inorganic & Nuclear)

no abstracts in English

Oral presentation

Spin transport in metallic antiferromagnetic textures; Interplay of inter-sublattice mixing and s-d exchange interaction

Ieda, Junichi; Yamane, Yuta*; Sinova, J.*

no journal, , 

Recently, antiferromagnetic (AFM) materials are generating more attention due to their potential to become a key player in technological applications. To understand spin transport in AFM metals, however, in addition to the s-d exchange interaction that plays a pivotal role in ferromagnetic-based spintronics, the sublattice degree of freedom should be taken into account. In this presentation we theoretically demonstrate electric voltage generation due to spinmotive forces originating from domain wall motion and magnetic resonance in antiferromagnets. This work suggests a new way to observe and explore the dynamics of antiferromagnetic textures by electrical means, an important aspect in the emerging field of antiferromagnetic spintronics. We also formulate spin-transfer torques in antiferromagnetic materials. Taking in the electron-magnetization exchange coupling and the inter-sublattice electron dynamic as model parameters, we examine the two limiting cases where either one of the two is dominant over another. Our work offers a framework for quantitative understanding of spin-transfer torques in different classes of antiferromagnetic materials.

Oral presentation

Rashba magnetic anisotropy in antiferromagnets

Ieda, Junichi; Maekawa, Sadamichi

no journal, , 

We study magnetic anisotropy in antiferromagnets (AFMs) with the inversion symmetry breaking (ISB). Magnetic anisotropy determines an energy barrier that separates preferable orientations of staggered magnetization in AFMs, and in its sense, understanding and controlling the magnetic anisotropy energy (MAE) in AFMs are fundamentally important for devising magnetic memory bits that should be reliably robust against any external (thermal, magnetic field, and electric current) noises. It has also been pointed out that a large value of MAE in AFMs is advantageous for the exchange bias field that is routinely used to fix magnetization direction at the AFM/FM interface in current magnetic memory technology. In this work, we employ two representative models for the AFMs and obtain the MAE as a consequence of the cooperation of the Rashba spin-orbit (RSO) and exchange interactions. For the global ISB model the MAE shows a transition depending on the magnitude of the RSO coupling: the easy-plane magnetic anisotropy is favored with the small RSO coupling whereas the perpendicular magnetic anisotropy (PMA) is induced with the large RSO coupling. For the local ISB the PMA is generally results in, which contrasts to the corresponding ferromagnetic case in which the condition for the PMA depends on the band structure and dimensionality. These features are particularly important for stabilizing the direction of the order parameter in AMF nanostructures and for electrical-field control of the MAE via the externally modulated RSO coupling.

Oral presentation

Magnetic anisotropy due to the Rashba effect in antiferromagnets

Ieda, Junichi; Maekawa, Sadamichi

no journal, , 

Recently spintronics phenomenon based on antiferromagnets has drawn much attention. In 2014, we proposed a mechanism that the Rashba spin-orbital interaction produces magnetic anisotropy due to competition with magnetic exchange interaction in a ferromagnetic thin film. This time the theory is extended to antiferromagnet with the Rashba spin-orbital interaction. Conduction electron spin that hops between the nearest neighbor sites on a lattice with antiferromagnetic order in two sublattice is considered. Two kinds of lattice models which feel an on-site exchange interaction and the Rashba interaction of (a) the same sign for the nearest neighbor hopping, or (b) the different sign for the next nearest neighbor hopping are investigated. Former is a model of the Rashba effect occurring at the interface between the antiferromagnetic thin film and another substance and the latter is for the Rashba effect in the antiferromagnet in which the inversion symmetry locally broken, such as CuMnAs. For each model, the angle dependence of the total energy on the antiferromagnetic order-parameter direction is obtained and the expression of the uniaxial magnetic anisotropy constant is derived. In model (a), it is shown that transition from easy plane anisotropy to perpendicular magnetic anisotropy occurs with increasing Rashba interaction. On the other hand, in model (b), it is shown that Rashba interaction always favors the perpendicular magnetic anisotropy as a result of competition with exchange interaction.

Oral presentation

Manipulation of antiferromagnetic magnetization by electron spins

Ieda, Junichi; Yamane, Yuta*; Jairo, S.*; Maekawa, Sadamichi

no journal, , 

no abstracts in English

Oral presentation

Theory of spin-transfer torques in antiferromagnetic textures

Ieda, Junichi; Yamane, Yuta*; Sinova, J.*

no journal, , 

Oral presentation

Noncolinear spin dynamics

Ieda, Junichi

no journal, , 

no abstracts in English

Oral presentation

Rashba PMA in AFMs

Ieda, Junichi

no journal, , 

no abstracts in English

19 (Records 1-19 displayed on this page)
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