THERMALLY ACTIVATED MAGNETIZATION REVERSAL IN ELONGATED FERROMAGNETIC PARTICLES

Elongated ferromagnetic single-domain particles are believed to exhibit a high stability of their remanent magnetization. However, here it is shown that for elongated particles thermal fluctuations lower the coercivity much more drastically than predicted by current theories. The rate for magnetization reversal is calculated for a classical model of a ferromagnet that allows for a spatially nonuniform magnetization distribution along the sample. The prefactor of the Arrhenius factor is explicitly evaluated and analytical results are obtained in the experimentally important limit of external magnetic fields close to the anisotropy field and for moderate damping.