Unconventional exchange bias effect driven by phase separation in basically antiferromagnetic Sm_0.1Ca_0.6Sr_0.3MnO₃

Magnetic investigations, focused on the uncommon behavior of the exchange bias (EB) effect, have been performed for basically antiferromagnetic (AFM) electron doped manganite Sm_0.1Ca_0.6Sr_0.3MnO₃. The studied system in the ground state exhibits a heterogeneous spin configuration consisting of the C-type antiferromagnetic phase with the Néel temperature T_N-C ≈ 150 K, the G-type AFM phase with the Néel temperature T_N-G ≈ 70 K, and a FM-like phase with very weak spontaneous magnetic moment. The phase separation, into two different AFM phases and a FM-like phase at the temperatures below T_N-G, leads to unusual magnetic properties, such as: narrowing of magnetic hysteresis loops in field cooling process, unconventional EB effect associated with spontaneous magnetization at temperatures below T_N-C, strong magnetic field dependence of the negative exchange bias at fields below 100 Oe turning into practically field independent one for fields above 0.5 kOe, significant shift of EB with temperature with a change of the sign from negative at 10 K to positive above 40 K. The atypical magnetic properties are discussed and related to two different interfaces appearing between coexisting magnetic phases.