20,735 research outputs found
Infrared spectroscopy under multi-extreme conditions: Direct observation of pseudo gap formation and collapse in CeSb
Infrared reflectivity measurements of CeSb under multi-extreme conditions
(low temperatures, high pressures and high magnetic fields) were performed. A
pseudo gap structure, which originates from the magnetic band folding effect,
responsible for the large enhancement in the electrical resistivity in the
single-layered antiferromagnetic structure (AF-1 phase) was found at a pressure
of 4 GPa and at temperatures of 35 - 50 K. The optical spectrum of the pseudo
gap changes to that of a metallic structure with increasing magnetic field
strength and increasing temperature. This change is the result of the magnetic
phase transition from the AF-1 phase to other phases as a function of the
magnetic field strength and temperature. This result is the first optical
observation of the formation and collapse of a pseudo gap under multi-extreme
conditions.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev.
Anisotropic Electronic Structure of the Kondo Semiconductor CeFe2Al10 Studied by Optical Conductivity
We report temperature-dependent polarized optical conductivity
[] spectra of CeFeAl, which is a reference material
for CeRuAl and CeOsAl with an anomalous magnetic
transition at 28 K. The spectrum along the b-axis differs
greatly from that in the -plane, indicating that this material has an
anisotropic electronic structure. At low temperatures, in all axes, a shoulder
structure due to the optical transition across the hybridization gap between
the conduction band and the localized states, namely -
hybridization, appears at 55 meV. However, the gap opening temperature and the
temperature of appearance of the quasiparticle Drude weight are strongly
anisotropic indicating the anisotropic Kondo temperature. The strong
anisotropic nature in both electronic structure and Kondo temperature is
considered to be relevant the anomalous magnetic phase transition in
CeRuAl and CeOsAl.Comment: 5 pages, 4 figure
Infrared optical absorption spectra of CuO single crystals: Fermion-spinon band and dimensional crossover of the antiferromagnetic order
We have obtained mid-infrared optical absorption spectra of the S=1/2 quasi
one-dimensional CuO using polarized transmission measurement and interpreted
the spectra in terms of phonon assisted magnetic excitations. When the electric
field is parallel to the main antiferromagnetic direction a Delta shaped peak
is observed with the maximum at 0.23eV which is attributed to spinons along
Cu-O chains. At low temperatures in the antiferromagnetic phase another peak
appears at 0.16eV which is attributed to two-magnon absorption but the spinon
peak remains. This behavior is interpreted as due to a dimensional crossover
where the low temperature three-dimensional magnetic phase keeps short range
characteristics of a one-dimensional magnet.Comment: 5 pages, 5 figure
Current distribution inside Py/Cu lateral spin-valve device
We have investigated experimentally the non-local voltage signal (NLVS) in
the lateral permalloy (Py)/Cu/Py spin valve devices with different width of Cu
stripes. We found that NLVS strongly depends on the distribution of the
spin-polarized current inside Cu strip in the vicinity of the Py-detector. To
explain these data we have developed a diffusion model describing spatial (3D)
distribution of the spin-polarized current in the device. The results of our
calculations show that NLVS is decreased by factor of 10 due to spin
flip-scattering occurring at Py/Cu interface. The interface resistivity on
Py/Cu interface is also present, but its contribution to reduction of NLVS is
minor. We also found that most of the spin-polarized current is injected within
the region 30 nm from Py-injector/Cu interface. In the area at Py-detector/Cu
interface, the spin-polarized current is found to flow mainly close on the
injector side, with 1/e exponential decay in the magnitude within the distance
80 nm.Comment: 10 pages, 14 figure
Magnetic Interaction in the Geometrically Frustrated Triangular Lattice Antiferromagnet
The spin wave excitations of the geometrically frustrated triangular lattice
antiferromagnet (TLA) have been measured using high resolution
inelastic neutron scattering. Antiferromagnetic interactions up to third
nearest neighbors in the ab plane (J_1, J_2, J_3, with
and ), as well as out-of-plane coupling (J_z, with
) are required to describe the spin wave dispersion
relations, indicating a three dimensional character of the magnetic
interactions. Two energy dips in the spin wave dispersion occur at the
incommensurate wavevectors associated with multiferroic phase, and can be
interpreted as dynamic precursors to the magnetoelectric behavior in this
system.Comment: 4 pages, 4 figures, published in Phys. Rev. Let
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