Temperature-induced magnetization reorientation in arrays of magnetic dots on a magnetic substrate

Abstract

We studied magnetic properties of regular arrays of magnetic dots on a magnetic layer. We took into account the exchange interaction, the dipolar interaction of amplitude D between spins, and the perpendicular anisotropy A. The spins are of the classical Heisenberg model. Due to the competition between D and A, the ground state (GS) can be perpendicular or parallel to the substrate. We have studied the body-centered-cubic and hexagonal-close-packed dot lattices. We have determined the GS magnetic structure as a function of A and D by a steepest descent method. The results show that below (above) a critical value of D/A, the GS spin configuration is perpendicular (parallel). We have studied finite-temperature properties of our system of dots in the vicinity of the critical D/A by Monte Carlo simulations. The obtained results show spectacular features, in particular on the spin reorientation. A phase diagram in the vinicity of the critical value of D/A is presented.