CONTRIBUTION OF THE FE2+ ION TO THE MAGNETIC ANISTROPY CONSTANT IN FERRITES

The magnetic anisotropy constant K1 originating from the presence of Fe2+ ions in ferrites is calculated, using the theory of Wolf, for a case that the electron hopping between Fe2+ and Fe3+ ions is allowed within a cluster of iron ions around some lattice defects. The calculated value of K1 exhibits a characteristic temperature dependence, i.e. the change of the sign from positive at lower temperatures to negative at higher temperatures. It is shown that the result well agrees with the Fe2+ contribution to K1 estimated from the available data of the anisotropy constant for the Ni1−xFe2+xO4 system. Copyright © 1978 WILEY‐VCH Verlag GmbH & Co. KGaA