MAGNETIC PHASE-DIAGRAM OF A THIN-FILM WITH A REORIENTATION TRANSITION

We study the magnetic state of a thin film undergoing a reorientation transition, in the plane defined by the temperature T and the thicknes s N. In going beyond free spin wave theory, three distinct regions are found: one with perpendicular magnetization; one with in-plane magnet ization and a third (high T)-region with no magnetization. We are able to determine the boundaries between these regions and the resulting p hase diagram agrees with the existing experimental data. A possible ma ximum in the reorientation transition T(R)(N) is predicted. Further ex perimental work is necessary to check this possibility.