The Spin Reorientation Transition and Phase Diagram of Ultrathin

MARIANELLA CARUBELLI; ORLANDO V. BILLONI; SANTIAGO PIGHIN; SERGIO A. CANNAS; DANIEL A. STARIOLO; FRANCISCO A. TAMARIT

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Año: 2008 vol. 77 p. 134417 - 134417

0163-1829

We show results from Monte Carlo simulations of a two dimensionalHeisenberg model for ultrathin films with perpendicular anisotropy.A complete phase diagram is obtained as a function of anisotropy andtemperature, spanning a wide range of behavior. We discuss our results inrelation with experimental findings in different ultrathin films.We observe andcharacterize a line of Spin Reorientation Transitions . Thistransition from out of plane stripe order to in plane ferromagnetic orderpresents a paramagnetic gap in between in a finite region in parameterspace, as reported in experiments. Forlarge anisotropies direct transitions from a low temperature stripephase to a paramagnetic or tetragonal phase with dominantperpendicular magnetization is observed, also in agreement with experiments.We also show the phase diagram for a system without exchange, i.e. withpure dipolar andanisotropy interactions. It shows a similar behavior to the ferromagneticcase with antiferromagnetic instead of stripe phases at low temperatures. ASpin Reorientation Transition is also found in this case.