Absolute Magnetic Susceptibilities by the Gouy and the Thorpe-Senftle Methods

Using the Curie-Cheneveau principle, A. Thorpe and F. E. Senftle have developed an absolute yet simple force method for measuring the magnetic susceptibilities of very small samples. In our laboratory an apparatus was constructed so that absolute susceptibilities could be determined by both the Thorpe-Senftle and the Gouy methods down to liquid helium temperatures. Measurements were made on powdered samples of the same batch of (NH4)2OsBr6, HgCo(SCN)4, and Fe(NH4)2(SO4)2·6H2O. Comparable accuracies were obtained by the two methods; however, about 3 ×10^-2 as much sample is required to do a Thorpe-Senftle measurement.