Studies of the Dynamical Jahn-Teller Effect on Static Magnetic Susceptibility

Abstract

Static magnetic susceptibilities of simplified model vibronic systems where non-Kramers paramagnetic ions in triplet ground state interact either with localized tetragonal modes of vibration with sharp frequency spectrum at ω (localized model), or with tetragonal modes composed of the superposition of phonons with continuous frequency spectrum (Debye model) are calculated in a rigorous way.
The susceptibility is simply expressed in terms of a temperature dependent reduction factor γ_L(T) for the localized model, or γ_D(T) for the Debye model, which diminishes the effective Curie constant and makes the susceptibility deviate from the Curie-Weiss law.
The theory explains the characteristic features of the susceptibilities of dilute solid solutions of UO₂ in ThO₂ measured by Slowinski and Elliott and by Comly, for example, the convex curvature of reciprocal susceptibility vs. temperature plot. The values of parameters determined to fit the observed susceptibilities are reasonable in orders of magnitude.