Low temperature properties of magnetic films

The effect of surface oxides on the low temperature magnetic properties of permalloy films is reviewed. Emphasis is placed on the work of Hagedorn and Mitchell and coworkers. It is shown that the unidirectional anisotropy in permalloy (typically exhibited at temperatures below 40 °K) can be correlated with the presence of -Fe₂O₃ as detected in electron diffraction studies. A possible mechanism for the phenomena is discussed which hinges on the depression of the Morin transition in -Fe₂O₃ as a consequence of a change in thed spacing of the -Fe₂O₃.The author would like to thank Professors L. D. Roberts and C. S. Smith of the University North Carolina for their helpful discussions during the course of this work.