Crossover-behavior of the saturation magnetic fields of (100) and (110) Fe/Cr/Fe trilayers

We use a simple and realistic theoretical model to investigate the saturation magnetic fields of ultrathin (100) and (110) Fe/Cr/Fe trilayer system. We consider the Fe films presenting magneto-crystalline anisotropies (cubic and uniaxial) and interacting through bilinear and biquadratic exchange couplings. From the equilibrium configurations, which are determined by the absolute minimum of the magnetic energy, we were able to set up field-dependent phase diagrams for the situation where the external static magnetic field H   is applied in the plane of the films at an arbitrary angle θHθH. We have obtained the critical frontier between the saturated and non-saturated phases. Two main results should be pointed out: (i) the change of the symmetry axis according to the magneto-crystalline fields and (ii) a sudden change (on a multicritical point) of the character of the magnetic phase transitions, typical of a crossover behavior.