Effective anisotropy due to the surface of magnetic nanoparticles

Abstract

Analytical solution has been found for the second-order effective anisotropy of magnetic nanoparticles of a cubic shape due to the surface anisotropy (SA) of the Néel type. Similarly to the spherical particles, for the simple cubic lattice the grand-diagonal directions $\left(\pm 1,\pm 1,\pm 1\right)$ are favored by the effective cubic anisotropy but the effect is twice as strong. Uniaxial core anisotropy and applied magnetic field cause screening of perturbations from the surface at the distance of the domain-wall width and reduce the effect of SA near the energy minima. However, screening disappears near the uniaxial energy barrier, and the uniform barrier state of larger particles may become unstable. For these effects the analytical solution is obtained as well, and the limits of the additive formula with the uniaxial and effective cubic anisotropies for the particle are established. Thermally-activated magnetization-switching rates have been computed by the pulse-noise technique for the stochastic Landau-Lifshitz equation for a system of spins.

12 pages, 8 figures

References in corpus (5)

• Effective anisotropies and energy barriers of magnetic nanoparticles with Neel surface anisotropy
• 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
• Pulse-noise approach for classical spin systems
• Surface effects on ferromagnetic resonance in magnetic nanocubes

Cited by in corpus (4)

• Magnetization nutation induced by surface effects in nanomagnets
• Energy balance and energy correction in dynamics of classical spin systems
• Spatial magnetization profile in spherical nanomagnets with surface anisotropy: Green's function approach
• Single-particle versus collective effects in assemblies of nanomagnets: screening