Effect of exchange interaction on superparamagnetic relaxation

Abstract

We use Langer's approach to calculate the reaction rate of a system of two (classical) spins interacting via the exchange coupling $J$ in a magnetic field $H$, with uniaxial anisotropy of constant $K$. We find a particular value of the exchange coupling, that is $j\equiv J/K=j_c\equiv 1-h^2$, where $h\equiv H/2K$, which separates two regimes corresponding to a two-stage and one-stage switching. For $j\gg j_c$ the Néel-Brown result for the one-spin problem is recovered.

7 pages, 2 eps figures, fig.1 of better quality can be provided upon request

References in corpus (2)

• Surface contribution to the anisotropy of magnetic nanoparticles
• Relaxation time of weakly interacting superparamagnets

Cited by in corpus (8)

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• Surface-induced cubic anisotropy in nanomagnets
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• AC susceptibility of an assembly of nanomagnets: combined effects of surface anisotropy and dipolar interactions
• Thermal and surface anisotropy effects on the magnetization reversal of a nanocluster
• Magnetization dynamics of two interacting spins in an external magnetic field
• Dynamics of a magnetic dimer with exchange, dipolar and Dzyalozhinski-Moriya interaction
• Surface-induced reduction of the switching field in nanomagnets