Magnetic resonances in powder-samples of quasi-one-dimensional anisotropic S = 1 spin systems

EPR experiments were performed on powder samples of the quasi-one-dimensional S = 1 spin systems NENC and TMNIN in the frequency range 55-400 GHz in magnetic fields up to 14 T. In both materials broad and asymmetric line shapes were observed pointing to a strong planar anisotropy. We interpreted the measured line shapes using a single-ion Hamiltonian. Transition matrix elements and occupation number of energy levels are taken into account in these calculations. In this way we obtain a good estimate for both the planar anisotropy D and the in-plane anisotropy E. (C) 1998 Elsevier Science B.V. All rights reserved.