Crystal and magnetic structure of copper chromite

Copper chromite, CuCr~O 4, is a tetragonally distorted normal spinel with a c/a ratio, as referred to a face-centered unit cell, of about 0.91. A structure which is physically reasonable, belonging to the space group D~-I42d, is based on an environment for the copper ions which is distorted from a tetr~hedron toward a square, and also slightly rotated about the c axis. The chromium ions are slightly displaced from their ideal positions. The magnetic neutron diffraction pattern, below a Curie point at about 135 K., indicates a triangular arrangement of moments such as one of those proposed by Yafet & Kittel.