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The Magnetic Susceptibility of Non-Interacting Nanoparticles

L. A. Ponomarenko·A. de Visser·E. Brück·A. M. Tishin
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Abstract

We have calculated the low-field magnetic susceptibility $χ$ of a system consisting of non-interacting mono-dispersed nanoparticles using a classical statistical approach. The model makes use of the assumption that the axes of symmetry of all nanoparticles are aligned and oriented at a certain angle $ψ$ with respect to the external magnetic field. An analytical expression for the temperature dependence of the susceptibility $χ(T)$ above the blocking temperature is obtained. The derived expression is a generalization of the Curie law for the case of anisotropic magnetic particles. We show that the normalized susceptibility is a universal function of the ratio of the temperature over the anisotropy constant for each angle $ψ$. In the case that the easy-axis is perpendicular to the magnetic field the susceptibility has a maximum. The temperature of the maximum allows one to determine the anisotropy energy.

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L. A. Ponomarenko, A. de Visser, E. Brück, A. M. Tishin. 2001-04-27. The Magnetic Susceptibility of Non-Interacting Nanoparticles. https://arxiv.org/abs/cond-mat/0104539

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