Colossal increase in negative magnetization, exchange bias and coercivity in samarium chromite due to a strong coupling between Sm³⁺–Cr³⁺spins sublattices

Abstract

We report giant temperature dependent negative magnetization (magnetization reversal) along with a large exchange bias and large coercivity in SmCrO3. The static magnetization measurements show the negative magnetization below ~192 K, due to competition between the external field, thermal activation energy and antiparallel Sm3+–Cr3+ spin interaction. At further lower temperatures, Sm3+ spins show an increased alignment due to the internal induced field of Cr3+ spins with minimum magnetization ~ − 0.037 emu g−1. The temperature dependent exchange bias shows non-monotonic behavior. At 35 K, the exchange bias ceases to exist due to the orientation of Sm3+ moments with respect to canted Cr3+ moments. The crossover temperature decreases from ~191 K at 100 Oe to ~153 K at 250 Oe. The training effect further confirms the exchange bias in SmCrO3. The dynamic magnetization measurements exhibit anomalies around spin reorientation transition (TSR ~ 34 K) and Neel transition (TN ~ 192 K) which is consistent with static measurement and no frequency dependence was observed. The room temperature Raman spectra of SmCrO3 show peaks at ~364, ~375 and ~456 cm−1 suggesting O-Cr-O bending modes within the octahedral.