247 research outputs found
Evidence for the singlet-dimer ground state in an S = 1 antiferromag netic bond alternating chain
Susceptibility, ESR and magnetization measurements have been performed on si
ngle crystals of an S=1 bond alternating chain compound: [Ni(333-tet)(\mu-NO
_2)](ClO_4) (333-tet = N,N'-bis(3-aminopropyl)propane-1,3-diamine) and the c
ompound doped with a small amount of Zn. We observed an anomalous angular de
pendence in the Zn-doped sample. These behaviors are well explained by the m
odel based on the VBS picture for the singlet-dimer phase. The picture impli es
that the free spins of S=1 with a positive single-ion anisotropy are indu ced
at the edges of the chains without forming the singlet-dimer.Comment: RevTeX, 14pages (preprint.sty) with 5figures, submitted to Phys. R
ev. Let
Direct observation of spin-quadrupolar excitations in SrCoGeO by high field ESR
Exotic spin-multipolar ordering in spin transition metal insulators has so
far eluded unambiguous experimental observation. A less studied, but perhaps
more feasible fingerprint of multipole character emerges in the excitation
spectrum in the form of quadrupolar transitions. Such multipolar excitations
are desirable as they can be manipulated with the use of light or electric
field and can be captured by means of conventional experimental techniques.
Here we study single crystals of multiferroic SrCoGeO, and show
that due to its nearly isotropic nature a purely quadrupolar bimagnon mode
appears in the electron spin resonance (ESR) spectra. This non-magnetic
spin-excitation couples to the electric field of the light and becomes
observable for a specific experimental configuration, in full agreement with a
theoretical analysis of the selection rules.Comment: 19 pages, 13 figures, , accepted for publication in Phys. Rev.
Spin-orbit torque generation in bilayers composed of CoFeB and epitaxial SrIrO grown on an orthorhombic DyScO substrate
We report on the highly efficient spin-orbit torque (SOT) generation in
epitaxial SrIrO(SIO), which is grown on an orthorhombic DyScO(110)
substrate. By conducting harmonic Hall measurement in
CoFeB (CoFeB)/SIO bilayers, we characterize two kinds of
the SOTs, i.e., dampinglike (DL) and fieldlike ones to find that the former is
much larger than the latter. By comparison with the Pt control sample with the
same CoFeB thickness, the observed DL SOT efficiency of SIO
(0.32) is three times higher than that of Pt (0.093). The
is nearly constant as a function of the CoFeB thickness,
suggesting that the SIO plays a crucial role in the large SOT generation. These
results on the CoFeB/SIO bilayers highlight that the epitaxial SIO is promising
for low-current and reliable spin-orbit torque-controlled devices.Comment: arXiv admin note: text overlap with arXiv:2305.1788
Spin current generation from an epitaxial tungsten dioxide WO
We report on efficient spin current generation at room temperature in rutile
type WO grown on AlO(0001) substrate. The optimal WO
film has (010)-oriented monoclinically distorted rutile structure with metallic
conductivity due to 5 electrons, as characterized by x-ray
diffraction, electronic transport, and x-ray photoelectron spectroscopy. By
conducting harmonic Hall measurement in NiFe/WO bilayer, we
estimate two symmetries of the spin-orbit torque (SOT), i.e., dampinglike (DL)
and fieldlike ones to find that the former is larger than the latter. By
comparison with the NiFe/W control sample, the observed DL SOT
efficiency of WO (+0.174) is about two thirds of that of W
(-0.281) in magnitude, with a striking difference in their signs. The magnitude
of the of WO exhibits comparable value to those of widely
reported Pt and Ta, and Ir oxide IrO. The positive sign of the
of WO can be explained by the preceding theoretical study
based on the 4 oxides. These results highlight that the epitaxial
WO offers a great opportunity of rutile oxides with spintronic
functionalities, leading to future spin-orbit torque-controlled devices.Comment: 14 pages, 4 figure
Supersymmetric Bianchi class A models
The canonical theory of supergravity is applied to Bianchi class A
spatially homogeneous cosmologies. The full set of quantum constraints are then
solved with the possible ordering ambiguity taken into account by introducing a
free parameter. The wave functions are explicitly given for all the Bianchi
class A models in a unified way. Some comments are made on the Bianchi type IX
cases.Comment: 9 pages, LaTeX, TIT/HEP-221/COSMO-3
Thermodynamic properties of a tetramer ferro-ferro-antiferro-antiferromagnetic Ising-Heisenberg bond alternating chain as a model system for Cu(3-Clpy)(N)
Thermodynamic properties of a tetramer
ferro-ferro-antiferro-antiferromagnetic Ising-Heisenberg bond alternating chain
are investigated by the use of an exact mapping transformation technique. Exact
results for the magnetization, susceptibility and specific heat in the zero as
well as nonzero magnetic field are presented and discussed in detail. The
results obtained from the mapping are compared with the relevant experimental
data of Cu(3-Clpy)(N) (3-Clpy=3-Chloropyridine).Comment: 10 pages, 1 table, 14 figures, to be presented at CSMAG04 conferenc
- …