INFLUENCES OF SURFACE IRON OXIDE LAYER ON MAGNETIC PROPERTIES OF IRON PIGMENT.

Mossbauer spectroscopy and other methods used to study the oxide layer on the surface of fine Fe particles. On the basis of X-ray and electron diffraction results, the surface oxide phase is characterized as consisting of extremely fine spinel crystals of Fe//3 O//4 and gamma - Fe//2 O//3 , and mixtures of these. Comparisons of the Mossbauer spectra under strong magnetic fields (25 and 50 kOe) of different samples indicates that the surface oxide layer is only very slightly magnetized; the internal field in the surface oxide layer is as much as 30 to 50 kOe lower than in the Fe material. While the surface oxide layer has the local magnetic properties of a spinel phase, the oxide layer makes almost no contribution to the Fe particle magnetic properties.