Integral Relaxation Time of Single-Domain Ferromagnetic Particles

TL;DR

This paper analytically calculates the integral relaxation time of noninteracting single-domain ferromagnetic particles under a magnetic field, revealing how potential well depletion affects relaxation dynamics at low temperatures.

Contribution

It provides an analytical expression for the integral relaxation time considering the effects of magnetic field and temperature, highlighting the interplay of overbarrier and intrawell relaxation.

Findings

au_{int}^{-1} deviates from \Lambda_1 at low temperatures.

Depletion of the upper potential well influences relaxation.

Integral relaxation time includes contributions from both overbarrier and intrawell processes.

Abstract

The integral relaxation time \tau_{int} of thermoactivating noninteracting single-domain ferromagnetic particles is calculated analytically in the geometry with a magnetic field H applied parallel to the easy axis. It is shown that the drastic deviation of \tau_{int}^{-1} from the lowest eigenvalue of the Fokker-Planck equation \Lambda_1 at low temperatures, starting from some critical value of H, is the consequence of the depletion of the upper potential well. In these conditions the integral relaxation time consists of two competing contributions corresponding to the overbarrier and intrawell relaxation processes.