EFFECTS OF A MAGNETIC-FIELD ON SPIN REORIENTATION IN BIGA-TMIG FILMS

Ferromagnetic resonance (FMR) and fixed magnetic field magnetization m easurements have been performed from 4.2 K to roam temperature to exam ine a second order phase transition involving the rotation of the easy direction of the magnetization in BiGa:TmIG epitaxial single crystal films. Magnetization measurements indicate that in zero magnetic field , a reorientation of the easy direction of magnetization occurs over a temperature range of 100 to 125 K. Over this temperature range the ea sy direction shifts from in-plane below 100 K to normal to the plane a bove 125 K. Additional magnetization measurements in fixed applied mag netic fields indicate that the reorientation region is magnetic field dependent. FMR results suggest that the transition may be described by a competition between the second order uniaxial, fourth order uniaxia l and first order cubic crystalline anisotropy energies. The FMR measu rements show a temperature range for the transition from 140 to 180 K rather than the range of 100 to 125 K indicated previously by zero fie ld magnetization measurements. The implications of the field dependenc e of the transition to the reorientation is discussed.