Shigeki Onoda

Crossover behavior of the anomalous hall effect and anomalous nernst effect in itinerant ferromagnets

The anomalous Hall effect (AHE) and anomalous Nernst effect (ANE) are experimentally investigated in a variety of ferromagnetic metals including pure transition metals, oxides, and chalcogenides, whose resistivities range over 5 orders of magnitude. For these ferromagnets, the transverse conductivity sigma{xy} versus the longitudinal conductivity sigma{xx} shows a crossover behavior with three distinct regimes in accordance qualitatively with a recent unified theory of the intrinsic and extrinsic AHE. We also found that the transverse Peltier coefficient alpha{xy} for the ANE obeys the Mott rule. These results offer a coherent and semiquantitative understanding of the AHE and ANE to an issue of controversy for many decades.

Bond electronic polarization induced by spin

We study theoretically the electric polarization induced by noncollinear spin configurations in the limit of strong Hund coupling. We employ a model of two magnetic ions sandwiching an oxygen ion. It is shown that there appears a longitudinal polarization

Mott transitions in the two-dimensional half-filled Hubbard model: Correlator projection method with projective dynamical mean-field approximation

{P}_{x}

Filling-control metal-insulator transition in the hubbard model studied by the operator projection method

along the bond, which is roughly proportional to

dx2-y2 Wave Pairing Fluctuations and Pseudo Spin Gap in Two-Dimensional Electron Systems

{({m}_{r}^{x})}^{2}ensuremath{-}{({m}_{l}^{x})}^{2}

Spin Hall effect of a conserved current : Conditions for a nonzero spin Hall current

where

Operator Projection Method Applied to the Single-Particle Green's Function in the Hubbard Model

{m}_{r(l)}^{x}

Theory of Non-Equilibirum States Driven by Constant Electromagnetic Fields— Non-Commutative Quantum Mechanics in the Keldysh Formalism —

is the

Chiral spin pairing in helical magnets.

x

Magneto-optical effect induced by spin chirality of the itinerant ferromagnet Nd2Mo2O7

component of the spin orientation vector at right (left) magnetic ion. A numerical study of the model Hamiltonian yields both longitudinal and transverse electric dipole moments. The transverse polarization is shown to have a nonuniform as well as a uniform component, with the latter being consistent with the previous theory. The longitudinal polarization is nonuniform and oscillating with the period half that of the spin order, but the local magnitude is typically much larger than the uniform transverse polarization and may be detected by x-ray/neutron scattering experiments.