62 research outputs found
Magnetoresistance of PrLaOsSb: Disentangling local crystalline-electric-field physics and lattice effects
Resistivity measurements were performed on PrLaOsSb
single crystals at temperatures down to 20 mK and in fields up to 18 T. The
results for dilute-Pr samples ( and 0.67) are consistent with model
calculations performed assuming a singlet crystalline-electric-field (CEF)
ground state. The residual resistivity of these crystals features a smeared
step centered around 9 T, the predicted crossing field for the lowest CEF
levels. The CEF contribution to the magnetoresistance has a
weaker-than-calculated dependence on the field direction, suggesting that
interactions omitted from the CEF model lead to avoided crossing in the
effective levels of the Pr ion. The dome-shaped magnetoresistance
observed for and 0.05 cannot be reproduced by the CEF model, and likely
results from fluctuations in the field-induced antiferroquadrupolar phase
First and second order magnetic and structural transitions in BaFeCoAs
We present here high resolution magnetization measurements on high-quality
BaFeCoAs, 0x0.046 as-grown single crystals.
The results confirm the existence of a magnetic tricritical point in the
(,) plane at x0.022 and reveal the emergence of the
heat capacity anomaly associated with the onset of the structural transition at
x0.0064. We show that the samples with doping near x
do not show superconductivity, but rather superconductivity emerges at a
slightly higher cobalt doping, x0.0315Comment: 4 pages, 5 figure
Exotic Kondo-hole band resistivity and magnetoresistance of CeLaOsSb alloys
Electrical resistivity measurements of non-magnetic single-crystalline
CeLaOsSb alloys, and 0.1, are reported for
temperatures down to 20 mK and magnetic fields up to 18 T. At the lowest
temperatures, the resistivity of CeLaOsSb has a
Fermi-liquid-like temperature variation , but with negative
in small fields. The resistivity has an unusually strong magnetic field
dependence for a paramagnetic metal. The 20 mK resistivity increases by 75%
between H=0 and 4 T and then decreases by 65% between 4 T and 18 T. Similarly,
the coefficient increases with the field from -77 to 29cmK between H=0 and 7 T and then decreases to 18cmK for 18 T. This nontrivial temperature and field variation
is attributed to the existence of a very narrow Kondo-hole band in the
hybridization gap, which pins the Fermi energy. Due to disorder the Kondo-hole
band has localized states close to the band edges. The resistivity for
has a qualitatively similar behavior to that of , but with a larger
Kondo-hole band
Universal magnetic and structural behaviors in the iron arsenides
Commonalities among the order parameters of the ubiquitous antiferromagnetism
present in the parent compounds of the iron arsenide high temperature
superconductors are explored. Additionally, comparison is made between the well
established two-dimensional Heisenberg-Ising magnet, KNiF and iron
arsenide systems residing at a critical point whose structural and magnetic
phase transitions coincide. In particular, analysis is presented regarding two
distinct classes of phase transition behavior reflected in the development of
antiferromagnetic and structural order in the three main classes of iron
arsenide superconductors. Two distinct universality classes are mirrored in
their magnetic phase transitions which empirically are determined by the
proximity of the coupled structural and magnetic phase transitions in these
materials.Comment: 6 pages, 4 figure
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