A class of ferrimagnetic oxide materials that have the garnet crystal structure. The crystal structure contains three types of nonequivalent sites in the oxygen lattice which are occupied by metal ions. The sites are referred to as 16(a), 24(c), and 24(d). A metal ion in a 16(a) site is surrounded by six oxygen ions which are at the corners of the octahedron. The metal ions in the 24(d) sites are found in nonregular tetrahedrons formed by oxygen ions, while the metal ions in the 24(c) sites have eight oxygen-ion nearest neighbors to form a triangular dodecahedron at the corners of a distorted cube.