Causes of the Metamagnetism in a Disordered EuMn{sub 0.5}Co{sub 0.5}O{sub 3} Perovskite

The magnetic properties of the EuMn{sub 0.5}Co{sub 0.5}O{sub 3} perovskite synthesized under various conditions are studied in fields up to 140 kOe. The sample synthesized at T = 1500°C is shown to exhibit a metamagnetic phase transition, which is irreversible below T = 40 K, and the sample synthesized at T = 1200°C demonstrates the field dependence of magnetization that is typical of a ferromagnet. Both samples have T{sub C} = 123 K and approximately the same magnetization in high magnetic fields. The metamagnetism is assumed to be related to a transition from a noncollinear ferromagnetic phase to a collinear phase, and the presence of clusters with ordered Co{sup 2+} and Mn{sup 4+} ions leads to ferromagnetism. The noncollinear phase is formed due to the competition between positive Co{sup 2+}–Mn{sup 4+} and negative Mn{sup 4+}–Mn{sup 4+} and Co{sup 2+}–Co{sup 2+} interactions, which make almost the same contributions, and to the existence of a high magnetic anisotropy.