Crystal Structure and the Magnetic Anisotropy of CuSO₄.5H₂O

Abstract

FROM a discussion of the magnetic susceptibilities of CuSO₄.5H₂O powder at different temperatures, Jordahl¹ concluded that the crystalline electric field acting on the Cu⁺⁺ ion in the crystal should be predominantly cubic in symmetry, and further, from the sign of the potential due to this field which fits the magnetic data, that the field should correspond to an octahedral distribution of six equal negative charges around the Cu^{+ +} ion. This result is not obvious from general structural considerations, since the crystal is triclinic, and there are five molecules of water and one SO₄ group associated with each Cu^{+ +} ion. The result, however, has been beautifully verified by the X-ray studies of Beevers and Lipson² on the structure of the crystal. The Cu^{+ +} ion is found to be at the centre of an octahedron of six negatively charged oxygen atoms. Four of them belong to four water molecules, and they form a square with the Cu^{+ +} ion in the centre. The other two, which are contributed by two sulphate groups, are located centrally above and below this square.