Investigations on the paramagnetism of crystals at low temperatures

Abstract

Although the investigation of the principal susceptibilities of paramagnetic crystals especially at low temperatures promises results of very great interest both from the theoretical and experimental standpoints, data on the subject are almost entirely wanting, probably at least in part as a result of the difficulty of making the necessary observations. Thus the only record of crystal susceptibilities as functions of the temperature is that of the measurement of the principal susceptibilities of siderose by Foëx, but these observations were not extended to lower temperatures than those obtainable with liquid air. The present preliminary note gives the results of an investigation of the principal susceptibilities of two crystals, namely, cobalt ammonium sulphate and nickel sulphate heptahydrate as functions of the temperature down to about 14° K. (melting point of hydrogen). These are thus the first observations of this type in the region of very low temperatures. The substances were chosen as representative of different classes of crystals (cobalt ammonium sulphate is monoclinic and nickel sulphate heptahydrate is rhombic), and as they promised results of special interest in the light of the phenomena shown by the mean susceptibilities obtained from measurements on the substances in powder form (see foregoing paper).