CRITICAL ANGLE OF LINEAR SPIN-WAVE SPECTRUM OF CAGE-YIG FILM

Linear spin wave spectra were measured as a function of the angle thet a between the sample normal and the direction of the applied magnetic field at temperatures between 140 K and RT, in charge uncompensated th in garnet film having the composition Y2.0Ca1.0Ge0.9Fe4.1O12 and reduc ed in FeCl2 or annealed in N-2. For the critical angle, we have found that the mode separation decreases with theta for theta < theta(c); at theta greater than or equal to theta(c) the spin wave modes collapse to a single line; and at theta --> theta(c) the mode intensities rise rapidly, verifying the theory (extended Portis VI model). The values o f A and epsilon were obtained from the data of separation and theta(c) . The results reveal that the Portis model dominates the spin wave exc itation in the reduced layer only at theta < theta(c).