Anomalous Relaxation in One-Dimensional Magnets.I : Long-Time t^<-1/2> Tail and Its Cutoff

概要

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In order to clarify various anomalies due to the long-time t^<-1/2> tail in one-dimensional Heisenberg magnets, a new theory of spin relaxation is formulated with the aid of the modecoupling continued-fraction representation of the time-correlation spectra. The absorption spectrum x"(ω) of ESR with a magnetic field along the chain is treated theoreby by summing up higher order fractions up to infinite order. Thus it turns out that a cutoff of the long-time t^<-1/2> tail arises from higher-order couplings to the spin diffusion process in such a way that the long-time t^<-1/2> tail exists only in the kinetic regime where ω_d(ω_d/ω_e)^<1/3>.<1/t≪ω_e with ω_d and ω_e being the characteristic frequency of the dipolar and the exchange interaction, respectively. The ESR line shape thus obtained has wings of the form ∣ω-ω_0∣^<-5/2> with a width of order ω_d(ω_d/ω_e)^<1/3> in agreement with experiments.
理論物理学刊行会の論文
1981-07-25