Multilayer samples and structures composed of NiO(t)/Co(2.5 nm)/NiO(t)/Py(2
.5 nm)/NiO( t) with t = 6.6 and 13.2 nm exhibit ferromagnetic interlayer co
upling below 400 K. A crossover is observed between the behavior near 300 K
and at 10 K in ferromagnetic(F)/antiferromagnetic(AF) structures. Effects
observed near 300 K, but not at 10 K, are an enhancement of Hc and the M-H
loop squareness in F/AF multilayers as one increases the number of layers.
A possible explanation for the crossover is given based on the domain wall
thickness becoming less than the AF film thickness. (C) 1999 American Insti
tute of Physics. [S0021-8979(99)67808-2].