Paramagnetic Dispersion Measurements at 77.3°K

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Abstract
The dispersion of the magnetic susceptibility of some paramagnetic compounds of Fe, Mn, and Cr, was studied at 77.3°K over a frequency range of 2 to 10 megacycles/sec. with magnetic fields up to 60,000 gauss. The results substantiate the theory of Casimir and du Pre, which is based upon the thermal coupling between the magnetic spin system and the lattice vibrations. The magnitude of the crystalline field splitting of the energy levels of the ground state was determined from the experimental results, for an assumed type of crystalline field and ionic arrangement. The splitting of chromic ammonium alum was found to differ from that of chromic potassium alum. The relaxation time for ferric ammonium alum was studied as a function of the magnetic field, and was found to fit an empirical formula which is based upon the theoretical conclusions of Van Vleck.