Interplay between surface anisotropy and dipolar interactions in an assembly of nanomagnets

Abstract

We study the interplay between the effects of surface anisotropy and dipolar interactions in monodisperse assemblies of nanomagnets with oriented anisotropy. We derive asymptotic formulas for the assembly magnetization taking account of temperature, applied field, core and surface anisotropy, and dipolar inter-particle interactions. We find that the interplay between surface anisotropy and dipolar interactions is well described by the analytical expression of the assembly magnetization derived here: the overall sign of the product of the two parameters governing the surface and the dipolar contributions determines whether intrinsic and collective terms compete or have synergistic effects on the magnetization. This is illustrated by the magnetization curves of $\gamma -F{e}_2{O}_3$ nanoparticles assemblies in the low concentration limit.

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References in corpus (7)

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• AC susceptibility of an assembly of nanomagnets: combined effects of surface anisotropy and dipolar interactions
• Effect of dipolar interactions and DC magnetic field on the specific absorption rate of an array of magnetic nanoparticles
• Ferromagnetic resonance of a magnetic dimer with dipolar coupling
• Ferromagnetic resonance of a two-dimensional array of nanomagnets: Effects of surface anisotropy and dipolar interactions
• Single-particle versus collective effects in assemblies of nanomagnets: screening