Suppressed and Accelerated Spin-Lattice Relaxation

The transient magnetic behavior of a paramagnetic substance, after an initial disturbance, is considered theoretically for a variety of situations in which the lattice temperature rises as a result of energy flow from the magnetic (electron spin) system. The direct and $T^9$ Raman spin-phonon processes are considered. Coupling between phonon modes, and leakage of energy into a bath are taken into account. Graphs of the resultant behavior are presented. Effects such as suppressed and accelerated spin relaxation, and rapid decay (phonon avalanche) after spin inversion, are discussed. It is pointed out that experiments performed without the usual helium bath may provide reliable measurements of inelastic phonon-boundary scattering.