Exchange bias in phase-segregated Nd2/3Ca1/3MnO3 as a function of temperature and cooling magnetic fields.

Exchange bias (EB) phenomena have been observed in Nd_2/3Ca_1/3MnO₃ colossal magnetoresistance perovskite below the Curie temperature T_C~70K and attributed to an antiferromagnetic-ferromagnetic (FM) spontaneous phase segregated state of this compound. Field cooled magnetic hysteresis loops exhibit shifts toward negative direction of the magnetic field axis. The values of exchange field H_EB and coercivity H_C are found to be strongly dependent of temperature and strength of the cooling magnetic field H_cool. These effects are attributed to evolution of the FM phase content and a size of FM clusters. A contribution to the total magnetization of the system due to the FM phase has been evaluated. The exchange bias effect decreases with increasing temperature up to T_C and vanishes above this temperature with disappearance of FM phase. Relaxation of a non-equilibrium magnetic state of the compound manifests itself through a training effect also observed while studying EB in Nd_2/3Ca_1/3MnO₃. [ABSTRACT FROM AUTHOR]