Investigations of Ferromagnetic Impurities. I

Abstract

A method has been developed whereby a permanent magnetic moment as small as 2 × ${10}^{-7\mathrm{}}$ per cc may be measured in any small solid specimen. Various materials were tested by this method for ferromagnetic impurities. To remove surface impurities it was necessary to dissolve away part of the specimen. Most metals then showed some volume impurity. In aluminum, however, the volume impurity was nonmagnetic but could be dissolved out and deposited on the surface in a ferromagnetic state. Measurements were also made on the magnetic hardness and hysteresis curves of the impurities; part of the impurity was found to be very "hard," with saturation incomplete at several thousand gauss and a coercive force∼100-200, and part quite "soft," with a relatively large initial susceptibility. Other properties of these impurities are being studied. The method was also extended to single crystals of dia- or para-magnetic materials whose magnetic anisotropy could be easily detected and measured.