5,501 research outputs found
Electronic phase separation due to magnetic polaron formation in the semimetallic ferromagnet EuB - A weakly-nonlinear-transport study
We report measurements of weakly nonlinear electronic transport, as measured
by third-harmonic voltage generation , in the low-carrier density
semimetallic ferromagnet EuB, which exhibits an unusual magnetic ordering
with two consecutive transitions at \,K and \,K. Upon cooling in zero magnetic field through the ferromagnetic
transition, the dramatic drop in the linear resistivity at the upper transition
coincides with the onset of nonlinearity, and upon further cooling is
followed by a pronounced peak in at the lower transition
. Likewise, in the paramagnetic regime, a drop of the material's
magnetoresistance precedes a magnetic-field-induced peak in nonlinear
transport. A striking observation is a linear temperature dependence of
. We suggest a picture where at the upper transition
the coalescing MP form a conducting path giving rise to a strong
decrease in the resistance. The MP formation sets in at around \,K below which these entities are isolated and strongly fluctuating, while
growing in number. The MP then start to form links at , where
percolative electronic transport is observed. The MP merge and start forming a
continuum at the threshold . In the paramagnetic temperature regime
, MP percolation is induced by a magnetic field, and the
threshold accompanied by charge carrier delocalization occurs at a single
critical magnetization.Comment: to appear in J. Kor. Phys. Soc (ICM2012 conference contribution
Evidence for electron-phonon interaction in FeMSb (M=Co, Cr) single crystals
We have measured polarized Raman scattering spectra of the
FeCoSb and FeCrSb (00.5)
single crystals in the temperature range between 15 K and 300 K. The highest
energy symmetry mode shows significant line asymmetry due to phonon
mode coupling width electronic background. The coupling constant achieves the
highest value at about 40 K and after that it remains temperature independent.
Origin of additional mode broadening is pure anharmonic. Below 40 K the
coupling is drastically reduced, in agreement with transport properties
measurements. Alloying of FeSb with Co and Cr produces the B mode
narrowing, i.e. weakening of the electron-phonon interaction. In the case of
A symmetry modes we have found a significant mode mixing
Strong pinning of vortices by antiferromagnetic domain boundaries in CeCo(InCd)
We have studied the isothermal magnetization of
CeCo(InCd) with = 0.0075 and 0.01 down to 50 mK. Pronounced
field-history dependent phenomena occur in the coexistence regime of the
superconducting and antiferromagnetic phases. At low-fields, a phenomenological
model of magnetic-flux entry well explains implying the dominance of
bulk pinning effect. However, unless crystallographic quenched disorder is
hysteretic, the asymmetric peak effect (ASPE) which appears at higher fields
cannot be explained by the pinning of vortices due to material defects. Also
the temperature dependence of the ASPE deviates from the conventional scenario
for the peak effect. Comparison of our thermodynamic phase diagrams with those
from previous neutron scattering and magnetoresistance experiments indicates
that the pinning of vortices takes place at the field-history dependent
antiferromagnetic domain boundaries.Comment: 13 pages,4 figures, to be published in New Journal of Physic
- …