Low temperature irreversibility induced by thermal cycles on two prototypical phase separated manganites

TL;DR

This study investigates how repeated thermal cycles induce irreversibility in the electrical and magnetic properties of two phase-separated manganites, revealing microstructural effects that favor insulating phases.

Contribution

It demonstrates that thermal cycling causes irreversible changes in manganites' properties, linked to phase coexistence and microstructural strain, which can be mitigated by magnetic field and pressure.

Findings

Resistivity increases after thermal cycling.

Magnetization decreases after thermal cycling.

Changes are partially reversible with magnetic field and pressure.

Abstract

We have studied the effect of irreversibility induced by repeated thermal cycles on the electric transport and magnetization of polycrystalline samples of La0.5Ca0.5MnO3 and La0.325Pr0.3Ca0.375MnO3. An increase of the resistivity and a decrease of the magnetization at different temperature ranges after cycling is obtained in the temperature range between 300 K and 30 K. Both compounds are known to exhibit intrinsic submicrometric coexistence of phases and undergo a sequence of phase transitions related to structural changes. Changes induced by thermal cycling can be partially inhibited by applying magnetic field and hydrostatic pressure. Our results suggest that the growth and coexistence of phases with different structures gives rise to microstructural tracks and strain accommodation, producing the observed irreversibility. Irrespective of the actual ground state of each compound, the effect of thermal cycling is towards an increase of the amount of the insulating phase in both compounds.