Magnetic Relaxation in an Exactly Soluble Model

Some nonequilibrium properties of an impurity in a linear chain of spins with nearest-neighbor interaction of the isotropic $X\ensuremath{-}Y$ type are studied. It is shown that under certain conditions its behavior is in agreement with the general principles of statistical mechanics. The relaxation in the presence of a transverse field is also studied, and it is found that in the weak coupling region the approach to equilibrium is described by a sum of exponentials. However, the results do not agree with the solution of the Bloch equations.

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