A. Taldenkov | Searcharxiv

arXiv2005

Metal-insulator transition in manganites: mixture of oxygen isotopes versus magnetic field

We have investigated the effect of oxygen isotope substitution on the metal-insulator transition temperature and the resistivity of the narrow band manganite (La0.25Pr0.75)0.7Ca0.3MnO3 in a constant magnetic field. A set of 16 samples having different mixtures of 16O, 17O and 18O isotopes with average mass varying from 16.0 to 17.8 a.m.u. was studied. We have found that the magnetoresistance and the isotope effect can be linked together with a single parameter - effective magnetic field, which decreases linearly with an increase of average oxygen mass with a slope of -2 T/a.m.u. The applicability of the small polaron model is discussed.

cond-mat.str-el↗

arXiv2001

Nonmonotonic Temperature Dependence of the Thermal Hall Angle of a YBa$_{2}$Cu$_{3}$O$_{6.95}$ Single Crystal

We have performed high-resolution measurements of the magnetic field (0~T~$ \le B \le 9~$T) and temperature (10 K~$\le T < 140~$K) dependence of the longitudinal and transverse Hall thermal conductivity of a twinned YBa$_{2}$Cu$_{3}$O$_{6.95}$ single crystal. We have used and compared two recently published methods to extract the thermal Hall angle $θ_H(T,B)$. Our results indicate that $\cot(θ_H)$ varies quite accurately as $T^4$ in the intermediate temperature range $\sim 0.3 < T/T_c$. It shows a well defined minimum at $T_m \simeq 20~$K which resembles that observed in the $c$-axis microwave conductivity. The electronic part of the longitudinal and the transverse thermal conductivity show the scaling behavior for transport properties predicted for d-wave superconductors in the temperature range $\sim 18~$K~$\le T \le 30~$K.

cond-mat.supr-con↗