The Measurement of Magnetic Induction in High Magnetic Fields at Low Temperatures. CoSO4·7H2O

Abstract

A discussion of the potentiometric method of measuring magnetic induction has been given for isothermal, isentropic, and isoerstedic processes. The magnetic properties of CoSO₄·7H₂O have been investigated over the range 1.2° to 78°K and in fields up to 93 kgauss. Values of the differential isothermal magnetic susceptibility and intensity of magnetization as a function of field have been given. Within the limits of error, the system may be considered to consist of a major component which is a function of H/T, and a small temperature independent component with a negative field dependence. The entropy of magnetization calculated from the temperature coefficient of the magnetic work has been compared with the previously published directly determined values. The saturation value of powdered CoSO₄·7H₂O has been found to be 11800 gauss cm³ mole^—1, and the Curie constant, T_{χα,m(initial)}=1.964 deg cm³ mole^—1, each for the magnetic component which is a function of H/T. The temperature‐independent susceptibility including diamagnetism has been represented by χ_β,m=(0.011₃—2.5×10^—8 H_i) cm³ mole^—1, with H_i in gauss. A correction has been applied to the earlier initial‐susceptibility measurements of Fritz and Giauque and their results are in agreement with the present data within their limit of accuracy.