Lattice effects, stability under a high magnetic field, and magnetotransport properties of the charge-ordered mixed-valenceLa0.35Ca0.65MnO3perovskite

Abstract

The highly ${\mathrm{Mn}}^{+4\mathrm{}}$-doped compound ${\mathrm{La}}_{0.35}{\mathrm{Ca}}_{0.65}{\mathrm{MnO}}_3$ has been studied up to high temperature (700 K) by using thermal-expansion, magnetostriction, magnetoresistance, and neutron-diffraction techniques. From 700 K down to room temperature the electrical conduction takes place through thermally activated hopping of polarons with $E_{\mathrm{hop}}$=45 meV. At the charge-ordering (CO) transition temperature $T_{\mathrm{CO}}$=275 K, pronounced anomalies in the resistivity and the lattice are observed. The neutron thermodiffractogram clearly establishes that the CO state occurs in the paramagnetic (P) phase and is accompanied by a large anisotropic lattice distortion with a simultaneous large distortion of the ${\mathrm{MnO}}_6$ octahedra. The antiferromagnetic (AF) phase appears at $T_N$=160±3 K. At this temperature no lattice effect is observed. The CO-P and the CO-AF ground states are stable under an applied magnetic field up to 12 T.