We have observed a new cross relaxation mechanism in the presence of a pure nuclear quadrupole splitting. This process involves two simultaneous nuclear spin flips and dramatically changes the form of the magnetization recovery curves at low temperature. We present a model which combines this mechanism with spin-lattice relaxation. The addition of cross relaxation allows us to explain nonmonotonic features that were previously not understood in the recovery curves of Sc nuclei in a variety of samples.

• Received 5 August 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.3835