Investigations of Ferromagnetic Impurities. II

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Abstract
Continuing previous studies on minute ferromagnetic impurities in ordinary metals, an attempt was made to render such impurities non-magnetic through heat treatment. In the case of copper and brass it was found that heating to 900°C and 750°C, respectively, in hydrogen for two hours or more, followed by quenching, would eliminate the ferromagnetism. This method was not successful with silver. These results are interpreted in terms of the crystal structures of the metals and of iron, which is believed to be the chief magnetic impurity. In the case of copper, reheating to 900°C in an atmosphere containing oxygen caused the ferromagnetism to return strongly. This is explained as due to the diffusion of the oxygen into the copper at high temperatures. The effect of heat treatment at other intermediate temperatures on the magnetic hardness and hysteresis of the impurity was also investigated.