Magnetic anisotropy of cobalt nanoparticle 2D arrays grown on corrugated MnF_2(110) and CaF_2(110) surfaces

摘要

Cobalt nanoparticle 2D arrays with different effective thicknesses of cobalt layer (2 nm < d_(eff) < 10 nm) were grown by molecular beam epitaxy on CaF_2(l10)/Si(0 01) and MnF_2(11 0)/CaF_2(11 0)/Si(0 01) substrates with corrugated morphology of the surface. Surface morphology analysis showed that for effective thickness of cobalt layer d_(eff)=5 nm the lateral dimensions of cobalt islands are about 5-10 nm and the distances between the islands differs in a half along and across the grooves. In both types of the heterostructures the shape of hysteresis loops measured by LMOKE depend on orientation of in-plane magnetic field relative to the direction of the grooves. The azimuthal dependence of coercive field H_c in Co/CaF_2(110)/Si(001) structures corresponds to Stoner-Wohlfarth model's predictions, which takes into account the anisotropy of individual particles. In contrast to that, in Co/MnF_2(1 1 0)/CaF_2(110)/Si(001) structures these dependences are analogous to those predicted by the model based on account of magnetic-dipole interaction between particles which are placed in chains (chain-of-spheres-model). Possible explanations of the difference in magnetic anisotropy are suggested.