Kinetic arrest of first-order transition between charge-ordered and ferromagnetic phases in Gd0.5Sr0.5MnO3 single crystals: magnetization relaxation studies

We have studied the span and nature of first-order phase transition (FOPT) between charge-ordered insulating and ferromagnetic metallic phases in oriented single crystals of Gd0.5Sr0.5MnO3. Magnetic field-temperature phase diagram was formulated from magnetization data for different crystal-lographic axes and non-monotonic variation of supercooling limit was observed at low temperature. A peculiar nature of magnetization was observed as irreversible open hysteresis loops during thermal cycling. We perceive that the nature of metastable states responsible for open hysteresis loops is different from that of supercooled ones. Further, thermal cycling magnetization data reveal that magnetic phases formed at 8 Kafter zero-field or field-cooled protocols (89 kOe) are not in equilibrium. Relaxation time constant is found to increase below 30 Kin magnetization relaxation measurements made across the FOPT. The non-monotonic variation of relaxation time constant is a manifestation of kinetic arrest of the FOPT. We propose that the non-equilibrium, glass-like magnetic phase (at 8 K and 89 kOe) is a consequence of kinetic arrest.