141 research outputs found
Spin-polaron model: transport properties of EuB
To understand anomalous transport properties of EuB, we have studied the
spin-polaron Hamiltonian incorporating the electron-phonon interaction.
Assuming a strong exchange interaction between the carriers and the localized
spins, the electrical conductivity is calculated. The temperature and magnetic
field dependence of the resistivity of EuB are well explained. At low
temperature, magnons dominate the conduction process, whereas the lattice
contribution becomes significant at very high temperature due to the scattering
with the phonons. Large negative magnetoresistance near the ferromagnetic
transition is also reproduced as observed in EuB.Comment: 4 pages, 3 figures, accepted in Phys. Rev.
Transport properties of moderately disordered UCuPd
We present a detailed study on the (magneto)transport properties of as-cast
and heat treated material UCuPd. We find a pronounced sample dependence of
the resistivity of as-cast samples, and reproduce the annealing
dependence of . In our study of the Hall effect we determine a metallic
carrier density for all samples, and a temperature dependence of the Hall
constant which is inconsistent with the Skew scattering prediction. The
magnetoresistive response is very small and characteristic for spin disorder
scattering, suggesting that overall the resistivity is controlled mostly by
nonmagnetic scattering processes. We discuss possible sources for the
temperature and field dependence of the transport properties, in particular
with respect to quantum criticality and electronic localization effects.Comment: 11 pages, 9 figures, submitted PR
Nature of the spin dynamics and 1/3 magnetization plateau in azurite
We present a specific heat and inelastic neutron scattering study in magnetic
fields up into the 1/3 magnetization plateau phase of the diamond chain
compound azurite Cu(CO)(OH). We establish that the
magnetization plateau is a dimer-monomer state, {\it i.e.}, consisting of a
chain of monomers, which are separated by dimers on the
diamond chain backbone. The effective spin couplings K
and K are derived from the monomer and dimer
dispersions. They are associated to microscopic couplings K,
K and a ferromagnetic K, possibly as
result of orbitals in the Cu-O bonds providing the superexchange
pathways.Comment: 5 pages, 4 figure
Metallic ground state and glassy transport in single crystalline URhGe: Enhancement of disorder effects in a strongly correlated electron system
We present a detailed study of the electronic transport properties on a
single crystalline specimen of the moderately disordered heavy fermion system
URhGe. For this material, we find glassy electronic transport in a
single crystalline compound. We derive the temperature dependence of the
electrical conductivity and establish metallicity by means of optical
conductivity and Hall effect measurements. The overall behavior of the
electronic transport properties closely resembles that of metallic glasses,
with at low temperatures an additional minor spin disorder contribution. We
argue that this glassy electronic behavior in a crystalline compound reflects
the enhancement of disorder effects as consequence of strong electronic
correlations.Comment: 5 pages, 4 figures, accepted for publication in PR
Spin glass behavior in URh_2Ge_2
URh_2Ge_2 occupies an extraordinary position among the heavy-electron
122-compounds, by exhibiting a previously unidentified form of magnetic
correlations at low temperatures, instead of the usual antiferromagnetism. Here
we present new results of ac and dc susceptibilities, specific heat and neutron
diffraction on single-crystalline as-grown URh_2Ge_2. These data clearly
indicate that crystallographic disorder on a local scale produces spin glass
behavior in the sample. We therefore conclude that URh_2Ge_2 is a 3D
Ising-like, random-bond, heavy-fermion spin glass.Comment: 10 pages, RevTeX, with 4 postscript figures, accepted by Physical
Review Letters Nov 15, 199
Giant spin canting in the S = 1/2 antiferromagnetic chain [CuPM(NO3)2(H2O)2]n observed by 13C-NMR
We present a combined experimental and theoretical study on copper pyrimidine
dinitrate [CuPM(NO3)2(H2O)2]n, a one-dimensional S = 1/2 antiferromagnet with
alternating local symmetry. From the local susceptibility measured by NMR at
the three inequivalent carbon sites in the pyrimidine molecule we deduce a
giant spin canting, i.e., an additional staggered magnetization perpendicular
to the applied external field at low temperatures. The magnitude of the
transverse magnetization, the spin canting of 52 degrees at 10 K and 9.3 T and
its temperature dependence are in excellent agreement with exact
diagonalization calculations.Comment: 5 pages, 6 Postscript figure
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