Colossal magnetoresistance in Gd1/2Sr1/2MnO3

Colossal magnetoresistance has been observed in polycrystalline Gd0.5Sr0.5MnO3 perovskite. Irreversibility and sharp anomalies in the magnetostriction, magnetization, and magnetoresistance isotherms take place at low temperatures (<90 K), which have been attributed to the establishment of a charge-ordered state (CO). For temperatures lower than approximate to 42 K, the CO state coexists with a cluster-glass state, as deduced from the magnetic and specific heat behavior and neutron scattering experiments. The linear-thermal-expansion measurements show an abrupt drop for T approximate to T-CO when a sufficiently high magnetic field is applied. The appearance of this anomaly has been attributed to the partial delocalization of the carriers by the field. (C) 1998 American Institute of Physics.