The mechanism of the magnetic interaction in the beta phase of the p-(nitro)phenyl nitronyl nitroxide (KAXHAS). A bottom-up study using only ab initio data

摘要

The magnetism of the beta phase of p-(nitro)phenyl nitronyl nitroxide (KAXHAS) crystal has been studied using a recently developed theoretical approach 'J. Phys. Chem. A 106 (2002) 1299'. This approach is a bottom-up study based on the evaluation of the magnetic interaction between all pairs of radicals (J(AB)), which allows the definition of the magnetic structure of the crystal. With only such knowledge, one solves an algebraic Heisenberg Hamiltonian on a properly chosen finite subset of the magnetic structure and then computes the magnetic susceptibility chi(T) and/or heat capacity C-p(T) curves for the crystal. This method is applied here to the KAXHAS crystal. The theoretical chi(T) and C-p(T) results are in very good agreement with the available experimental data. This theoretical methodology is first reviewed here on physical terms, and then used to rationalize the bulk ferromagnetic behavior of KAXHAS in terms of its corresponding microscopic J(AB) pair interactions. (C) 2003 Elsevier Science Ltd. All rights reserved. [References: 36]