Linear Antiferromagnetic Interaction in Organic Free Radicals

Abstract

Abstract The static magnetic susceptibilities from 1.8°K to 300°K, and the ESR spectra from 1.5°K to 300°K, of several organic free radicals have been measured on powder samples. The broad maxima in the susceptibility which indicate the antiferromagnetic interaction and the broadening of the ESR absorption lines have been observed. The data are analysed on the basis of the linear Heisenberg model and shown to be consistent with the one-dimensional magnetic chain model of isotropic exchange interaction. Discussions are made of the grounds of susceptibility, the ESR, and the specific heat measurements. In addition to a short-range ordering of spins, the possibility of long-range ordering is also discussed in two radicals, BDPA-Bz and p-Cl-BDPA, on the basis of discontinuities in the slope of susceptibility, the rapid broadening of the ESR linewidth, and the disappearance of the ESR absorption.