Magnetic anisotropy of cobalt nanoparticle 2D arrays grown on corrugated MnF2(1 1 0) and CaF2(1 1 0) surfaces

Cobalt nanoparticle 2D arrays with different effective thicknesses of cobalt layer (2 nm < deff < 10 nm) were grown by molecular beam epitaxy on CaF2(1 1 0)/Si(0 0 1) and MnF2(1 1 0)/CaF2(1 1 0)/Si(0 0 1) substrates with corrugated morphology of the surface. Surface morphology analysis showed that for effective thickness of cobalt layer deff = 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 Hc in Co/CaF2(1 1 0)/Si(0 0 1) structures corresponds to Stoner–Wohlfarth modelʹs predictions, which takes into account the anisotropy of individual particles. In contrast to that, in Co/MnF2(1 1 0)/CaF2(1 1 0)/Si(0 0 1) 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.