The Magnetic Anisotropy of α—NiSO4·6H2O between 13 and 295°K. A Torsion Balance for Magnetic Anisotropy Measurements

The magnetic anisotropy of single crystals of α—NiSO₄·6H₂O has been measured at temperatures between 13 and 295°K. Two crystals of different origin gave concordant results. The difference in magnetic susceptibility between directions parallel and perpendicular to the tetragonal crystallographic axis is given by ${\chi }_{\perp }{\mathrm{-\chi }}_{\Vert }{\text{=1.37×10}}^{\text{−5}}{\text{+1.502×10}}^{\text{−2}}{\text{/T+1.686/T}}^2$ . The susceptibility difference was independent of field strength up to 10,000 gauss over the temperature range investigated. The results are discussed in connection with the theoretical treatment of the susceptibility of nickel salts by Schlapp and Penney. A torsion balance for the magnetic anisotropy measurements is described.