Journal
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
Volume 316, Issue 2, Pages 248-254Publisher
ELSEVIER
DOI: 10.1016/j.jmmm.2007.03.212
Keywords
nanomagnetism; surface effects; classical models
Ask authors/readers for more resources
In a many-spin approach that takes account of the internal structure, microscopic interactions and single-site anisotropies, we investigate the effect of spin non-collinearities induced by the boundary and surface anisotropy on the behaviour of individual magnetic nanoparticles. Through analytical and numerical calculations, we show that there are mainly two regimes separated by some critical value of the surface-anisotropy constant K-s which controls the intensity of spin non-collinearities: (i) the so-called Stoner-Wohlfarth or Neel-Brown regime of a macrospin undergoing a coherent switching, and (ii) the many-spin regime where the strong spin non-collinearities invalidate the coherent mechanism, and where the particle's magnetic state and switching mechanisms can no longer be modelled by a macrospin. For small-to-intermediate values of K-s, and within two models of surface anisotropy (transverse and Neel), the behaviour of the nanoparticle can be modelled by that of a modified macrospin with an effective potential energy containing a uniaxial and cubic-anisotropy terms. This effective spin model provides a crossover between the two regimes above. (C) 2007 Elsevier B.V. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available