ANTIFERROMAGNETIC DOMAINS AND THE SPIN-FLOP TRANSITION OF MNF2

In antiferromagnetic MnF2 the magnetic moments of manganese are aligne d along the tetragonal axis of the rutile structure. In a magnetic fie ld H-SF along that axis (9.27 T at 4.2 K) the antiferromagnetic moment s flop in the basal plane. Polarized neutron diffraction measurements showed that at about H-SF the entire crystal becomes aligned in a sing le antiferromagnetic domain, which persists even after the field is su ppressed. The effect is due to a minute misalignment (a fraction of de gree) of the applied held with the tetragonal axis of the crystal. The ensuing breakdown of symmetry at the spin-flop transition provides a way to control domains in this type of antiferromagnet.