Tunable exchange bias in hard/soft SmMnO3/α-Mn2O3 composite with AFM structures

Abstract

Exchange bias effect was effectively generated in a novel hard/soft SmMnO3 (~93%)/α-Mn2O3 (~7%) composite, with two different antiferromagnetic (AFM) states. Below 40 K, the magnetization hysteresis loops exhibit both a negative horizontal shift and a positive vertical shift. The horizontal shift is attributed to the reversal of soft α-Mn2O3 biased by hard SmMnO3. The vertical shift originates from the different degree of magnetization reversal of Mn2O3 and SmMnO3. The vertical shift decreases with increasing measuring field and finally approaches zero, while the horizontal shift still exists. At 20 K and 10 K, both of the horizontal shift and the vertical shift increase gradually with increasing cooling field. The exchange bias effect is weakened at 30 K and finally vanishes at 40 K. All these rich features suggest that the exchange coupling can be effectively tuned in SmMnO3/α-Mn2O3 system. The possible mechanism of this interesting behaviour is also proposed.