SPATIALLY MODULATED ANTIFERROMAGNETIC ORDER IN COO/NIO SUPERLATTICES

Neutron diffraction measurements confirm the presence of long-range antiferromagnetic order in superlattices of cobalt oxide and nickel oxide. A single transition temperature between the values for bulk CoO and NiO is evident for two samples with 36 angstrom periods as previously reported, but the separate Ni and Co order parameters in a 72 angstrom period superlattice approximate bulk behavior. In the latter sample the magnetic order remains coherent across ostensibly paramagnetic CoO interlayers above 400 K. Mean field analysis accounts for the layer thickness dependence of the ordering temperature.