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Anisotropy in Ferromagnetic Nanoparticles: Level-to-Level Fluctuations of a Collective Effect

Gonzalo Usaj·Harold U. Baranger
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Abstract

We calculate the mesoscopic fluctuations of the magnetic anisotropy of ferromagnetic nanoparticles. A microscopic spin-orbit Hamiltonian considered as a perturbation of the much stronger exchange interaction first yields an explicit expression for the anisotropy tensor. Then, assuming a simple random matrix model for the spin-orbit coupling allows us to describe the fluctuation of such a tensor. In the case of uniaxial anisotropy, we calculate the distribution of the anisotropy constant for a given number of electrons, and its variation upon increasing this number by one. The magnitude of the latter is sufficient to account for the experimental data.

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Gonzalo Usaj, Harold U. Baranger. 2005-11-30. Anisotropy in Ferromagnetic Nanoparticles: Level-to-Level Fluctuations of a Collective Effect. https://doi.org/10.1209/epl%2Fi2005-10210-4

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