Size and Thermal Conductivity Effects in Paramagnetic Relaxation

Abstract

The Casimir-du Pré thermodynamic theory of paramagnetic relaxation is generalized by taking account of the thermal conductivity of the paramagnetic salt. The case of a spherical specimen in a constant temperature bath is considered. One finds that infinitely many times are required to characterize the relaxation when a magnetic field is suddenly applied. The alternating current susceptibility is calculated and is shown to contain terms depending on the size and thermal conductivity of the specimen. A limited comparison of the theory with experimental data is made.