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 th at 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 metamag netic behavior. At about T-M = 370 K, a transition from a semiconducti ve to a quasimetallic state has been observed. It is supposed that a f erromagnetic low-spin cobalt state occurs in the temperature range bet ween T-i and T-C.