Ja. Borchers et al., PROPAGATION OF ANTIFERROMAGNETIC ORDER ACROSS PARAMAGNETIC LAYERS IN COO NIO SUPERLATTICES/, Journal of applied physics, 73(10), 1993, pp. 6898-6900
Using neutron-diffraction techniques, we have probed the magnetic stru
cture of nickel-oxide/cobalt-oxide superlattices grown by reactive spu
ttering. Collinear antiferromagnetic order propagates through several
bilayers despite the short-range nature of the spin interaction in the
components. The magnetic order for 36 angstrom period superlattices d
evelops simultaneously in the NiO and CoO layers at a Neel temperature
between the values for bulk CoO and NiO. When the superlattice period
icity is increased to 72 angstrom, the Ni and Co spins appear to order
separately at temperatures shifted from their bulk T(N). The magnetic
coherence length decreases as the temperature is increased, but remai
ns greater than the width of a single bilayer above T(N) for the CoO i
nterlayers. Mean-field calculations demonstrate that exchange coupling
at the interfaces is responsible for the anomalous magnetic behavior
near the phase transition.