Spin Glass Behaviour and Spin-Dependent Scattering inLa0.7Ca0.3Mn0.9Cr0.1O3 Perovskites

Abstract

The magnetic, electrical and thermal transport properties of theperovskite La0.7Ca0.3Mn0.9Cr0.1O3have been investigated by measuring dc magnetization, acsusceptibility, the magnetoresistance and thermal conductivity in thetemperature range of 5–300 K. The spin glass behaviour with a spinfreezing temperature of 70 K has been well confirmed for this compound,which demonstrates the coexistence and competition between ferromagneticand antiferromagnetic clusters by the introduction of Cr. Colossalmagnetoresistance has been observed over the temperature rangeinvestigated. The introduction of Cr causes the ``double-bump'' featurein electrical resistivity ρ(T). Anomalies on thesusceptibility and the thermal conductivity associated with thedouble-bumps in ρ(T) are observed simultaneously. The imaginarypart of ac susceptibility shows a sharp peak at the temperature ofinsulating–metallic transition where the first resistivity bump wasobserved, but it is a deep-set valley near the temperature where thesecond bump in ρ(T) emerges. The thermal conductivity shows anincrease below the temperature of the insulating–metallic transition, butthe phonon scattering is enhanced accompanying the appearance of thesecond peak of double-bumps in ρ(T). We relate those observed inmagnetic and transport properties ofLa0.7Ca0.3Mn0.9Cr0.1O3 to the spin-dependent scattering. The results reveal that the spin–phononinteraction may be of more significance than the electron(charge)–phonon interaction in the mixed perovskite system.