Influence of Cu substitution for Mn on the structure, magnetic, magnetocaloric and magnetoresistance properties of La 0.7Sr 0.3MnO 3 perovskites

Abstract

Structural, magnetic, magnetocaloric and magnetoresistance (MR) studies on La 0.7Sr 0.3Mn 0.95Cu 0.05O 3 (No. 1) and La 0.7Sr 0.3Mn 0.9Cu 0.1O 3 (No. 2) perovskites are reported. The crystal structure of the samples is rhombohedral with a change of the lattice constants depending on the Cu content. FC and ZFC thermomagnetic measurements for both compositions at low field indicate that a spin–glass-like state (or cluster glass) occurs at low temperatures and a very sharp change of magnetization around the phase-transition point. The Curie temperature, T C, does almost not depend on the content of Cu substitution. A maximum magnetic-entropy change, Δ S ma x , of 1.96 and 2.07 J/kg K at 13.5 kOe and 350 K is observed for sample No. 1 and No. 2, respectively. Therefore, they can be considered as active magnetic refrigerant materials for room-temperature applications. Electrical-resistance measurements show that both samples are metallic conductor for T< T C and semiconductor for T> T C; moreover, the MR is maximal around T C.