A magnetic study of the iron-nickel-aluminium system

Abstract

The iron-nickel-aluminium ternary system has been brought into prominence in recent years on account of its application in the permanent magnet industry. A study of some magnetic properties of this system has been made by Köster (1932-3), but his work is largely concerned with features other than those dealt with by the writer. An exhaustive X-ray examination of these alloys has been carried out by Bradley and Taylor (1938), and the information obtained has been used to throw light on the permanent magnetism in this system (Bradley and Taylor 1937 a, b, c ). Through the collaboration of Dr Bradley the writer has been able to make magnetic investigations on the same specimens as were used in the X-ray analysis, and the present account deals with a survey of the variation of the saturation intensity of these alloys with temperature. Owing to the complexity of the magnetic properties of alloys in this system, it is essential that the more fundamental properties should be the subject of the first investigation. The properties of ferromagnetic materials in low magnetizing fields depend to a considerable extent upon heat treatment, whilst on the other hand the saturation intensity in high fields shows less variation, and is in some degree a measure of the number of elementary magnets, presumably electron spins, contributing to the ferromagnetic magnetization of the particular alloy. Furthermore, the variation of the saturation intensity with temperature should give indications of any structure changes which may occur. A new method for the rapid measurement of saturation intensities for a few milligrams of substance over a range of temperature has been evolved (Sucksmith 1939) and the method there described has been used in the investigation on the nickel-iron-aluminium system.