Temperature dependence of interlayer coupling and magnetization in amorphous-FeNiB/Ru multilayers

For amorphous-FeNiB (2.0 nm)/Ru multilayers, an oscillatory interlayer coupling is observed with the variation of the Ru spacer thickness. At 0.8 nm thick Ru layer, near the first antiferromagnetic coupling maximum, the energy of the effective interlayer coupling at low temperature T is found to change as a linear function of T3/2. At the same time, the spontaneous magnetization of the samples at low temperature scales as a linear function of T. Therefore, the temperature dependence of the energy of the effective coupling might be controlled by thermal spin waves in the ferromagnetic layers.