Nonsecular contribution to the decay of spin-echo signals of quadrupolar nuclei in magnetically ordered materials

We analyze the influence of fluctuations of the nonsecular part of the spin Hamiltonian on the decay of ordinary and multiquantum signals of the two-p ulse spin echo in a quadrupole spin system with an inhomogeneously broadene d spectral line. Expressions are obtained for the rate of decay of an echo in the case of selective excitation of a signal from quadrupole nuclei with arbitrary spin. These expressions are then used to analyze the experimenta lly observed ordinary and multiquantum echo signals from quadrupole nuclei with spin I=3/2 (Cr-53, Cu-63, and Cu-65) in ferromagnetic chromium chalcog enide spinels. (C) 1999 American Institute of Physics. [S1063-7761(99)02107 -1].