Phase transitions in the Gd0.5Ba0.5CoO3 perovskite

Magnetization measurements of a Gd0.5Ba0.5CoO3 perovskitelike compound have revealed an anomalous behavior at T-i = 240 K and T-C = 277 K that corresponds to appearing and disappearing spontaneous magnetization. The transition at T-i is accompanied by the jump of conductivity and a giant magnetoresistance. Below T-i, Gd0.5Ba0.5CoO3 exhibits metamagnetic behavior. At about T-M = 370 K, a transition from a semiconductive to a quasimetallic state has been observed. It is supposed that a ferromagnetic low-spin cobalt state occurs in the temperature range between T-i and T-C.