Detection of field-dependent antiferromagnetic domains in exchange-biased Fe3O4/NiO superlattices

Neutron diffraction studies of Fe3O4/NiO superlattices reveal that the fiel d dependence of domains in the antiferromagnetic NiO is correlated with the presence or absence of exchange biasing. Measurements of the full width at half maximum of the (111) NiO reflection show that after cooling in zero f ield, the antiferromagnetic domain size both parallel and perpendicular to the growth axis is sensitive to the strength of the applied field. In contr ast, after cooling from room temperature in a field of 5 T, the domain size is generally smaller than the zero-field-cooled value and does not vary wi th field. These data suggest that exchange biasing originates from domain w alls frozen into the antiferromagnet upon field cooling. (C) 2000 American Institute of Physics. [S0003-6951(00)00352-1].