Pressure-induced exchange bias effect in phase-separated CaMn0.9Ru0.1O3

Strong enhancement of exchange bias (EB) effect in phase-separated CaMn0.9Ru0.1O3 manganite with ferromagnetic phase heavily suppressed under pressure was observed in the measurements of field-cooled magnetization hysteresis loop. It was found that both EB field HE and normalized remanence asymmetry pronouncedly increase with increasing pressure P, enlarging by one order of magnitude at P = 10 kbar. In contrast, the coercive field HC shows a non-monotonic variation with pressure, reaching a maximum value at around 5 kbar. Such unusual HC(P) dependence may be explained by transformation from multi-domain to single-domain state in a system of ferromagnetic (FM) size-variable particles. Comparison of HE(P) with HC(P) data indicates remarkable enhancement of EB with decrease in HC in the pressure range between 5 and 10 kbar. It is argued that a strong increase of HE under pressure is attributed to the suppression of FM phase, i.e., to the decrease in size of FM clusters embedded in antiferromagnetic matrix. P...