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

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 (T_SR ∼ 34 K) and Nèel transition (T_N ∼ 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. (paper)