Magnetic anisotropy in EuS-PbS multilayers

We present the results of ferromagnetic resonance studies of the thickness dependence of magnetic anisotropy in 2 series of EuS-PbS multilayers grown on (111) BaF2 and (100) KCl substrates with the EuS thickness varying in the range d = 6-70 A. The anisotropy constant K was found to follow the dependence K(d) = Kv + 2Ks/d, with the surface term Ks larger for layers grown on BaF2 as compared to KCl. This difference is discussed in terms of different thermal stress-induced distortions of cubic crystal lattice of EuS. We found that the thickness of EuS layer required for the perpendicular (to the layer) magnetization is d = 2-3 A, i.e., it is below 1 monolayer.