Theoretical simulation of the anisotropic phases of antiferromagnetic thin films

We simulate antiferromagnetic thin films. Dipole-dipole and antiferromagnetic exchange interactions as well as uniaxial and quadrupolar anisotropies are taken into account. Various phases unfold as the corresponding parameters J, D, and C, as well as the temperature T and the number n of film layer, vary. We find (i) how the strength Delta(nu) of the anisotropy arising from dipole-dipole interactions varies with the number of layers nu away from the film's surface, with J and with n; (ii) a unified phase diagram for all n-layer films and bulk systems; (iii) a layer-dependent spin reorientation (SR) phase in which spins rotate continuously as T, D, C, and n vary; (iv) that the ratio of the SR to the ordering temperature depends (approximately) on n only through (D+Delta/n)/C, and hardly on J; (v) a phase transformation between two different magnetic orderings, in which spin orientations may or may not change, for some values of J, by varying n.