Pressure effect on Bi0.4Ca0.6Mn1-xRu xO3 manganite: Enhanced ferromagnetism and collapsed exchange bias

Abstract

Pressure effect on magnetic state of Ru-doped charge-ordered manganite Bi0.4Ca0.6Mn1 - xRu xO3 (x=0.1, 0.2) was investigated by magnetization measurements in the temperature range of 5-315 K and under pressure up to ∼10 kbar. It was found that the x=0.2 composition is basically ferromagnetic (FM) while the low-doped (x=0.1) one exhibits a FM cluster glass behavior and exchange bias (EB) effect at low temperatures. Bi0.4Ca 0.6Mn0.9Ru0.1O3 demonstrates a substantial pressure-enhanced ferromagnetism, evidenced by ∼70 increase in spontaneous magnetization at 10 K under 10.3 kbar. It appears that an applied pressure strongly increases the FM to antiferromagnetic (AFM) phase ratio in the sample, leading to a notable decrease in both coercive field HC and EB field HE (HC and HE at 10 K decrease under pressure of ∼10 kbar by about 40 and 50%, respectively). The pressure-induced changes are qualitatively described within the simple model for FM size-variable clusters embedded in an AFM matrix. It is argued that both Ru-doping and external pressure act similarly, leading to a growth of the FM phase volume. © 2012 American Institute of Physics.