Low-energy properties of two-dimensional magnetic nanostructures: interparticle interactions and disorder effects

P. J. Jensen; G. M. Pastor

doi:10.1088/1367-2630/5/1/368

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arXiv · cond-mat/0310303

Low-energy properties of two-dimensional magnetic nanostructures: interparticle interactions and disorder effects

P. J. Jensen·G. M. Pastor

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Abstract

The low-energy properties of two-dimensional ensembles of dipole-coupled magnetic nanoparticles are studied as function of structural disorder and particle coverage. Already small deviations from a square particle arrangement lift the degeneracies of the microvortex magnetic configuration, and result in a strongly noncollinear magnetic order of the particle ensemble. The energy distribution of metastable states is determined. For a low degree of disorder a strongly asymmetric shape with a pronounced peak of the ground state energy results. In contrast, for a strong disorder a Gaussian-like distribution is obtained. The average dipole coupling energy $\bar E_\mathrm{dip}$ decreases with increasing structural disorder. The role of vacancies has been studied for a square particle array by determining the angular distribution of the preferred microvortex angle as function of the vacancy concentration. Indications for a preferred angular direction along the axial as well as along the diagonal directions of the square array are revealed. A corresponding investigation for disturbed square arrays results in a different angular distribution. The effect of dipole-quadrupole corrections resulting from the finite size of the particles is quantified.

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P. J. Jensen, G. M. Pastor. 2003-10-14. Low-energy properties of two-dimensional magnetic nanostructures: interparticle interactions and disorder effects. https://doi.org/10.1088/1367-2630%2F5%2F1%2F368

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