Anisotropy in Ferromagnetic Nanoparticles: Level-to-Level Fluctuations of a Collective Effect
arXiv:cond-mat/0407771 · doi:10.1209/epl/i2005-10210-4
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.
arXiv comment7 pages, 3 figures, published version
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- Spin-Noise and Damping in Individual Metallic Ferromagnetic Nanoparticles
- Tunneling density of states in quantum dots with anisotropic exchange