Irreversibility induced by thermal cycles in phase separated manganites

BERNARDO SIEVERS; JOAQUIN SACANELL; MARIANO QUINTERO; LETICIA GRANJA; GRISELDA POLLA; PABLO LEVY; FRANCISCO PARISI

Barcelona

Conferencia; 20th International Conference on Magnetism; 2015

We have studied the effect of irreversibility induced by repeated thermal cycles on the magnetization of polycrystalline samples of La0.5Ca0.5MnO3 and La0.325Pr0.3Ca0.375MnO3. A decrease of the magnetization at different temperature ranges after cycling is obtained in the temperature range between 300 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. We observed that the 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 and produces 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 non ferromagnetic phase in both compounds. We developed a phenomenological model to describe the observed effect in terms of a growth of one phase against the other through the contact surface between them.