Distribution of metal ions and magnetic susceptibility in CuGaMnO4 spinel

Copper gallium manganite, CuGaMnO4, was synthesized and its single crystal structure and magnetic properties studied to determine cation distribution and valence stares of the transition metals. The compound exhibits fee spin el structure at room temperature and site occupation factors resulting from the structure refinement show dominating presence of Cu+ ions at the tetra hedral sites. All Ga3+ ions occupy 50% of octahedral positions, while the m anganese ions in Mn3+ and Mn4+ electronic states are distributed between th e tetrahedral and octahedral sites. Magnetic susceptibility, chi, and inver se susceptibility measured as a function of temperature show that at T-c = 21 K, a phase transition of ferrimagnetic nature takes place. The structura l and magnetic properties and an absence of the Jahn-Teller distortion were explained by the formula: (Cu0.7+Mn0.33+)[Cu0.32+Ga3+Mn0.74+]O-4. (C) 1999 Elsevier Science Ltd. All rights reserved.