A STUDY OF MAGNETITE AT 4.2K AND SUBJECT TO STRONG APPLIED MAGNETIC-FIELDS

Mossbauer spectra of a powdered sample of magnetite were taken at 4.2 K and in applied fields of 0-14 T. They were fitted in accordance with specific crystallographic models of magnetite below the Verwey transi tion. At least five octahedral Fe3+ sites and four octahedral Fe2+ Sit es are needed to obtain both good fits and parameters which vary consi stently with applied field strength. The Fe 2 +ions exhibit a large qu adrupole interaction, which leads to an applied-field subspectrum of u nusual shape. This shape is adequately represented by an analytic calc ulation for a randomly oriented electric field gradient and for magnet ic moments which are collinear with the applied field.