Crystal defects in manganese (II) oxide and their influence on antiferromagnetic behaviour

Abstract

Antiferromagnetic domain walls in synthetic MnO crystals are found by electron microscopy to exist at temperatures up to ∼ 25°K aboveT _N. Precipitates of Mn₃O₄ and dislocations associated with them impede the motion of walls and are the main cause of their retention aboveT _N. On cooling to belowT _N, such defects apparently can also provide the basis of a “memory” for the re-establishment of earlier domain configurations. Electron diffraction shows that the manganous oxide is non-stoichiometric and at room temperature possesses both short-range order and a superlattice (witha _sup=2a₀). The superlattice is believed to be magnetic in origin but the short-range order is manifest as structural microdomains, probably with ordering of cation vacancies. The microdomains occur as lamellae parallel to {111}, with an average thickness of 30 Å.