The measurement of magnetic saturation intensities at different temperatures

Abstract

The magnetic properties of alloy systems have assumed increasing importance in recent years. In view of the extreme complexity of the different magnetic characteristics of these alloys, it is evident that a consideration of the more fundamental properties constitute the essential starting point for a systematic investigation. Whilst the behaviour in low magnetic fields may depend largely upon thermal and mechanical treatment, the intensity is known to show less variation, particularly if sufficiently high fields are employed. In the case of many so-called “hard” magnetic materials, however, some thousands of gauss are necessary to produce complete alinement of the elementary domains. If, further, only small quantities are available, the magnetic field required to overcome the shape factor and saturate the material makes the use of an electromagnet essential. The intensity must be measured over a range of temperatures up to the Curie point, so that the variation in the moment of the elementary magnets accompanying a change in structure can be followed. None of the existing methods appears suitable for rapid measurements on a large number of magnetic materials. A new method has been developed capable of measurements on a few cubic millimetres of substance to a high degree of accuracy at any temperature, and it seemed worth while to deal with it in a separate communication.