Anomalous hysteresis in magnetoresistive ceramic and film samples of (La0.8Sr0.2)1−xMn1+xO3 (0⩽x⩽0.4)

Abstract

A study is made of the external structure, magnetization, and magnetoresistive effect in ceramic samples of (La0.8Sr0.2)1−xMn1+xO3 annealed at 1150 and 1500 °C. It is shown that the additional annealing at 1500 °C leads to significant changes in the magnetization and increases the magnetoresistive effect by a factor of 2–3, depending on x. An “anomalous” magnetic hysteresis is observed on the initial parts of the magnetization curves in both ceramic and laser-deposited film samples. It is found that the value of the “anomalous” magnetic hysteresis depends on the composition of the samples (on x) and their annealing temperature. A mechanism for the appearance of the “anomalous” hysteresis is proposed, involving the presence and interaction of ferromagnetic and antiferromagnetic phases.