Ultrafine maghemite particles: II. The spin-canting effect revisited

For pt.I. see ibid, vol.6, p.3081-90, (1994). The magnetic structure of ultrafine maghemite particles was studied by Mossbauer spectroscopy. We have compared the degree of spin alignment obtained in applied magnetic fields in particulate samples with different frozen-in orientational distributions of the easy directions of the magnetization. Full alignment of the spins was not obtained even in large applied fields (4.35 T). The degree of alignment with the applied field was found to be independent of the orientation of the easy directions in the sample when the applied field was larger than 0.75 T. This result shows that the incomplete alignment of the spins in ultrafine maghemite particles subjected to large applied fields is not due to incomplete alignment of the net particle magnetization due to large magnetic anisotropy, but rather stems from a canting of individual spins.