724 research outputs found
Magnetic digital flop of ferroelectric domain with fixed spin chirality in a triangular lattice helimagnet
Ferroelectric properties in magnetic fields of varying magnitude and
direction have been investigated for a triangular-lattice helimagnet
CuFe1-xGaxO2 (x=0.035). The magnetoelectric phase diagrams were deduced for
magnetic fields along [001], [110], and [1-10] direction, and the in-plane
magnetic field was found to induce the rearrangement of six possible
multiferroic domains. Upon every 60-degree rotation of in-plane magnetic field
around the c-axis, unique 120-degree flop of electric polarization occurs as a
result of the switch of helical magnetic q-vector. The chirality of spin helix
is always conserved upon the q-flop. The possible origin is discussed in the
light of the stable structure of multiferroic domain wall.Comment: 5 pages, 4 figures. Accepted in Phys. Rev. Let
Fast reaction limit of a three-component reaction–diffusion system
AbstractWe consider a three-component reaction–diffusion system with a reaction rate parameter, and investigate its singular limit as the reaction rate tends to infinity. The limit problem is given by a free boundary problem which possesses three regions separated by the free boundaries. One component vanishes and the other two components remain positive in each region. Therefore, the dynamics is governed by a system of two equations
Ferroelectricity induced by spin-dependent metal-ligand hybridization in BaCoGeO
We have investigated the variation of induced ferroelectric polarization
under magnetic field with various directions and magnitudes in a staggered
antiferromagnet BaCoGeO. While the ferroelectric polarization
cannot be explained by the well-accepted spin current model nor exchange
striction mechanism, we have shown that it is induced by the spin-dependent
- hybridization between the transition-metal (Co) and ligand (O) via the
spin-orbit interaction. On the basis of the correspondence between the
direction of electric polarization and the magnetic state, we have also
demonstrated the electrical control of the magnetization direction.Comment: 4 pages, 4 figure
Giant directional dichroism of terahertz light in resonance with magnetic excitations of the multiferroic oxide BaCoGeO
We propose that concurrently magnetic and ferroelectric, i.e. multiferroic,
compounds endowed with electrically-active magnetic excitations
(electromagnons) provide a key to produce large directional dichroism for long
wavelengths of light. By exploiting the control of ferroelectric polarization
and magnetization in a multiferroic oxide BaCoGeO, we demonstrate
the realization of such a directional light-switch function at terahertz
frequecies in resonance with the electromagnon absorption. Our results imply
that this hidden potential is present in a broad variety of multiferroics
Orbital Properties of Sr3Ru2O7 and Related Ruthenates Probed by 17O-NMR
We report a site-separated O-NMR study of the layered perovskite
ruthenate SrRuO, which exhibits nearly two-dimensional transport
properties and itinerant metamagnetism at low temperatures. The local hole
occupancies and the spin densities in the oxygen orbitals are obtained by
means of tight-binding analyses of electric field gradients and anisotropic
Knight shifts. These quantities are compared with two other layered perovskite
ruthenates: the two-dimensional paramagnet SrRuO and the
three-dimensional ferromagnet SrRuO. The hole occupancies at the oxygen
sites are very large, about one hole per ruthenium atom. This is due to the
strong covalent character of the Ru-O bonding in this compound. The magnitude
of the hole occupancy might be related to the rotation or tilt of the RuO
octahedra. The spin densities at the oxygen sites are also large, 20-40% of the
bulk susceptibilities, but in contrast to the hole occupancies, the spin
densities strongly depend on the dimensionality. This result suggests that the
density-of-states at the oxygen sites plays an essential role for the
understanding of the complex magnetism found in the layered perovskite
ruthenates.Comment: 9 pages, 5 figures, to be published in Phys. Rev.
Magnetic-field induced competition of two multiferroic orders in a triangular-lattice helimagnet MnI2
Magnetic and dielectric properties with varying magnitude and direction of
magnetic field H have been investigated for a triangular lattice helimagnet
MnI2. The in-plane electric polarization P emerges in the proper screw magnetic
ground state below 3.5 K, showing the rearrangement of six possible
multiferroic domains as controlled by the in-plane H. With every 60-degree
rotation of H around the [001]-axis, discontinuous 120-degree flop of P-vector
is observed as a result of the flop of magnetic modulation vector q. With
increasing the in-plane H above 3 T, however, the stable q-direction changes
from q|| to q||, leading to a change of P-flop patterns under
rotating H. At the critical field region (~3 T), due to the phase competition
and resultant enhanced q-flexibility, P-vector smoothly rotates clockwise twice
while H-vector rotates counter-clockwise once.Comment: 4 pages, 3 figures. Accepted in Physical Review Letter
Mechanisms of enhanced orbital dia- and paramagnetism: Application to the Rashba semiconductor BiTeI
We study the magnetic susceptibility of a layered semiconductor BiTeI with
giant Rashba spin splitting both theoretically and experimentally to explore
its orbital magnetism. Apart from the core contributions, a large
temperature-dependent diamagnetic susceptibility is observed when the Fermi
energy E_F is near the crossing point of the conduction bands, while the
susceptibility turns to be paramagnetic when E_F is away from it. These
features are consistent with first-principles calculations, which also predict
an enhanced orbital magnetic susceptibility with both positive and negative
signs as a function of E_F due to band (anti)crossings. Based on these
observations, we propose two mechanisms for an enhanced paramagnetic orbital
susceptibility.Comment: 4 figures; added reference
Anomalous Nernst Effect in Nonmagnetic Nodal Line Semimetal PbTaSe
PbTaSe is a unique topological material, in which the number of nodal
lines is expected to change at the structural transition between the lower
temperature/pressure "L" phase and the higher temperature/pressure "H" phase.
We report the anomalous Nernst effect attributed to the Berry curvature of
nodal lines and its change with the structural transition. In the L phase, the
Nernst coefficient () shows the step-like magnetic field dependence
reminiscent of the anomalous Nernst effect of nonmagnetic Dirac/Weyl
semimetals. By applying hydrostatic pressure, we discovered that the amplitude
of the anomalous component significantly decreases at the transition to the H
phase, which might correspond to the partial annihilation of nodal line
structures.Comment: 29 page, 14 figure
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