Magnetic Susceptibility of a Sintered Rod ofαMnS

Abstract

The magnetic susceptibility of a sintered sample of $\alpha \mathrm{MnS}$ was measured from 90°K to 550°K by an absolute Gouy method. The extrapolated susceptibility at 0°K was approximately equal to $\frac{7}{10}$ the maximum susceptibility at the Néel point (154°K). It was not possible to fit the data above the Néel point with a unique set of Weiss-Curie constants, probably due to the persistence of short-range ordering effects above the Néel temperature. Upon using the recent Wojtowicz application of the Ising-Bethe theory, a unique set of constants, $\frac{\tilde{J}}{k}=-100.5\mathrm{}°$K and $C_M=3.57\mathrm{}$, fitted the data satisfactorily between 175°K and 550°K. A diamagnetic correction of 58×${10}^{-6\mathrm{}}$ per mole was applied to the data before calculating the above values. Above the Néel point the susceptibility of the sintered specimen was less than the susceptibility of a powder sample by a factor which was too large to be explained in terms of the standard correction for powders or by differences in geometry. Multiple maxima in the susceptibility which were outside the range of experimental error were noted at 144°K, 151°K, 157°K, and 167°K. When considered in conjunction with the specific heat anomalies previously detected at 139°K and 147°K, it is suggested that a change in either spin ordering or crystal structure occurs in this temperature region and is responsible for the irregular susceptibility behavior.