Temperature and thickness dependence of coercivity and magnetization of Co/Cu and Co/Si multilayers

Co/Cu and Co/Si multilayers of total thickness ∼3000 A were prepared by rf and dc magnetron sputtering. The nominal thicknesses of the individual layers were in the range of 4 to 100 A. A large coercivity (Hc) at 10 K was observed for very thin layers of Co in Co/Cu samples, and it decreased with increase of the Co layer thickness. For very thin layers of Co in Co/Cu samples, the layer behaved superparamagnetically. Similar behavior was not to be observed in Co/Si samples. With increased substrate temperature (Ts) during deposition, Hc was also observed to increase (decrease) for Co/Cu (Co/Si) samples. Magnetization data were modeled to determine the diffusion layer thicknesses.