Nature of energy gaps in the spin wave spectrum due to induced transitions in Er Fe O3

The behaviour of energy gaps at the points spin-reorientation second order phase transition in Er Fe O3 induced by magnetic field has been studied experimentally. It has been found that at the point of termination of spin reorientation of iron sublattices the gap magnitude is independent of the field (temperature) and essentially increases as a result of the metamagnetic transition in the erbium subsystem. It has been concluded that in the former case longitudinal oscillations of iron magnetization are unessential and in the latter case longitudinal oscillations of erbium magnetization make a predominant contribution to increase of the gap