Acta Physica Academiae Scientiarum Hungaricae 6. (1957)

1956 / 2. szám - L. Pál - T. Tarnóczi: Temperature Dependence of the Differential Susceptibility of Cobalt in Strong Magnetic Fields

TEMPERATURE DEPENDENCE OF THE DIFFERENTIAL SUSCEPTIBILITY OF COBALT IN STRONG MAGNETIC FIELDS By L. PÁL and T. TarNOCZI CENTRAL RESEARCH INSTITUTE FOR PHYSICS, BUDAPEST (Presented by L. Jánossy. — Received 30, XII. 1955) A curve showing a characteristic double maximum was obtained for the temperature dependence of the differential susceptibility of cobalt in strong magnetic fields ; all sections of this curve could be interpreted on the basis of the theory of the rotation processes. The tempe­rature of the minimum between the two maxima calculated from Sucksmith and Thomson’s [13] measurement on monocrystals is found to be in good agreement with the temperature pertaining to the experimentally determined minimum of the differential susceptibility of a polycrystal­­line sample. The effect of the a ß phase transformation on the differential susceptibility is studied. Introduction In a state near magnetic saturation, the shape of the magnetization curve of polycrystalline materials free of external and internal mechanical strains is determined almost exclusively by the magnetic anisotropy. From this it is ob­vious that in strong magnetic fields differential susceptibility and magnetic anisotropy are most closely interrelated. It is to be expected that much below the Curie temperature, the temperature dependence of the differential suscep­tibility is determined by the temperature dependence of the anisotropy con­stants, as the latter generally vary with temperature to a much greater extent than the saturation magnetization. It follows that the study of the temperature dependence of the differential susceptibility in strong magnetic fields is likely to yield valuable information on the temperature dependence of the magnetic anisotropy constants. Admittedly, the most reliable means by which to deter­mine these constants and their temperature dependence is to make measurements on monocrystal specimens, yet in many cases it appears expedient to have these supplemented by similar measurements on polycrystalline specimens. For cu­bic ferromagnetic materials, a host of data [1 ] confirm good agreement between the anisotropy constants measured on monocrystals and those measured on poly crystalline materials. While the field and temperature dependence of the differential suscepti­bility of cubic polycrystalline materials near magnetic saturation (iron, nickel, and their alloys), has been studied by a great number of authors, relatively little attention has been paid to cobalt of hexagonal structure. Bloch [2], Weiss and Forrer [3], and Allen and Constant [4 ] did investigate the tempera- 5 Acta Physica VI/2

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