The Magnetic Anisotropy of Copper Sulphate Pentahydrate, CuSO4·5H2O, in Relation to its Crystal Structure. Part III.

Measurements have been made of the magnetic anisotropy of CuS${\mathrm{O}}_4$·5${\mathrm{H}}_2$O at different temperatures from 26°C to -190°C. The crystal is nearly uniaxial magnetically, and its two principal susceptibilities conform roughly to the Curie law, with different Curie constants. The observed anisotropy of the crystal may be attributed to the anisotropy induced in the ${\mathrm{Cu}}^{++}$ ion under the influence of the asymmetric electric field of the neighboring negatively charged atoms. From the known positions of these atoms the field should be expected to have tetragonal symmetry. The two principal susceptibilities of the ${\mathrm{Cu}}^{++}$ ion, along the tetragonal axis of the field, and perpendicular to the axis, respectively, are calculated. The corresponding effective magneton numbers are calculated therefrom, and it is found (1) that these magneton numbers vary little with temperature, and (2) that the magneton numbers corresponding to the two principal susceptibilities of the ion are widely different.