Anomalous re-entrant hysteresis loops and maximum of the coercive force have been found near 130 K in polycrystalline GdIG ferrite. A qualitative explanation of the observed phenomena is given. It is suggested based on the Snoek's model of magnetic after effect that Fe2 ion may be responsible for pinning the domain wall.

In ceramic samples of YIG, an anomalous behavior of photo-induced effect on permeability was observed at 77K: the peak at the beginning of xenon flash and then usual decrease in permeability were detected. This can be explained by the maximum of free electrons during flash time.