The low damping Neel relaxation time for fine ferromagnetic particles fromthe energy diffusion method of Kramers

The formula for the relaxation time of the magnetization of a single domain ferromagnetic particle in the low damping limit which has hitherto been de rived by the method of first passage times [I. Klik, L. Gunther, J. Stat. P hys. 60 (1990) 473] is derived by extending the low damping escape rate the ory (flux over barrier method) of Kramers [H.A. Kramers, Physica 7 (1940) 2 84], originally given for mechanical particles to spins, yielding a much si mpler calculation. The analogy with macroscopic mechanisms of polarization oscillations in H-bonded chains is emphasized. (C) 1999 Elsevier Science B. V. All rights reserved.