Magnetic Studies of Solid Solutions. I. Methods of Observations and Preliminary Results on the Precipitation of Iron from Copper

Abstract

This paper represents the first step in an extended program whose aim is the investigation of solid solutions with special reference to the structures that may be formed by heat treatment and plastic deformation. It is hoped to include eventually observations in high fields (100,000 gauss) and at low temperatures. The present work deals with observations up to 40,000 gauss and temperatures ranging from 20 to 1000°C. The manner of observation and reliability of the results is described in some detail. A series of observations on alloys of copper containing up to 0.7 percent iron are reported. Up to about 4 percent of iron can be put into solution in copper at high temperatures, but the solubility decreases to an exceedingly small value at room temperature. Our observations indicate that iron atoms in solution in copper retain a permanent magnetic moment of approximately 3.5 Bohr magnetons, and obey a Curie-Weiss law at high temperatures, the Curie temperature of an alloy containing 0.7 percent iron by weight being 150°K. The solution seems to be sluggish and can be greatly supercooled. The manner of precipitation from solution appears to be fairly complex, and the results are being tentatively interpreted as follows: First there is a rearrangement of the atoms in the solution followed by the precipitation of a nonmagnetic phase which can be converted into a ferromagnetic phase by cold work. This ferromagnetic phase can be made to grow thermally, but apparently does not form readily of its own accord.