Anisotropy of the electron spin-resonance linewidth of

This paper presents measurements of the angular variation of the position and width of ESR lines in three mutually perpendicular planes of a single crystal of in the temperature range 12 - 200 K at two widely differing microwave frequencies. The analysis is carried out in terms of the anisotropic exchange and anisotropic Zeeman interaction. The variations of the anisotropy of the linewidth can be attributed to a temperature dependence of the orientation and the principal values of the exchange tensor.