HALF-FIELD EPR TRANSITIONS IN THE 1D HEISENBERG PARAMAGNET TMMC

Half-field EPR-transitions have been observed and analysed in the transversal and longitudinal dynamical susceptibility of the quasi-one-dimensional (1D) Heisenberg magnet (CH3)4NMnCl3 (TMMC). Measurements were performed at room temperature in the frequency range from 9 to 70 GHz. In contrast to recent reports, both longitudinal and transversal transitions show a strong linewidth anisotropy similar to that of the normal EPR line, as has been expected from the mode-coupling theory of Lagendijk. The lineshape of these half-field transitions deviates significantly from that of the main line. The intensity ratio of both lines allows evaluation of the diffusion constant. © 1979.