Magnetic susceptibility, Mossbauer spectroscopy and powder neutron diffraction experiments have shown that iron(III) phosphate, FePO4, undergoes a novel spin reorientation transition at 17K between two antiferromagnetic phases. The ordered magnetic moments lie in the basal plane of the trigonal unit cell between the Neel temperature (24K) and 17K, below which temperature the spins align along the unique (c) axis.
