Investigations on magne-crystallic action v. paramegnetic salts of the rare earth and iron groups

Abstract

In Part II of this series (KHRISHNAN, CHAKRAVORTY and BANERJEE 1933) we gave an account of magnetic measurements on single crystals of several sulphates and double sulphates of the iron group, and in Part IV (KHRISHNAN and BANERJEE 1936) on crystals whose paramagnetic ions are all in the S-state, which are of special interest. The present Part describes further measurements, on a large number of paramagnetic crystals, among which are many rare earth salts, several double sulphates, double selenates, selenates, sulphato-selenates and fluoberyllates of the iron group, and a few feebly paramagnetic crystals like the chromates, dichromates and ferricyanides. The magnetic data are discussed on the basis of the theory developed by VAN VLECK, PENNEY and SCHLAPP (1932). The experimental method used in these measurements was the same as was described in our previous papers. The magnetic anisotropy of the crystal was measured by both the oscillational and rotational methods described in Part III (KRISHNAN and BANERJEE 1935) in connexion with the measurements on organic crystals. The values obtained by the two methods were practically the same, the latter method being slightly more convenient. The absolute susceptibility among some convenient direction in the crystal was measured by the modified Rabi method described in Part II. The double sulphates, double selenates, and sulphato-selenates were prepared by mixing aqueous solutions of the two components in suitable molecular proportions. The fluoberyllates were prepared by the method described by RAY in a recent paper (1932). The fluoberyllate of cobalt (CoBeF4), for example, was prepared in the following manner. First, cobalt nitrite was obtained by the double decomposition of barium nitrite and cobalt sulphate. It was mixed in solution with the required amount of ammonium fluoride. The solution was evaporated, and further heated to decomposition. Cobalt fluoride was left over, which when treated with beryllium fluoride yielded CoBeF4.. The double fluoberyllates were obtained by mixing aqueous solutions of the two component fluoberyllates in equimolecular proportions.