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Nanomagnetism: extension of the Stoner–Wohlfarth model within Néel's ideas and useful plots

Chuev, M A and Hesse, J (2007) Nanomagnetism: extension of the Stoner–Wohlfarth model within Néel's ideas and useful plots. Journal of Physics: Condensed Matter, 19 (50). 506201 (18pp).

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This paper deals with the extension of the well known Stoner–Wohlfarth (SW) model widely used to compare magnetic properties of real single-domain particle systems with its ideal predictions. The model is often discussed in connection with nanomagnetism. The extension of this successful SW model is gained by combining it with Néel's ideas concerning the dynamical behavior and relaxation of the magnetization in such systems. We present the derivation of a universal relaxation equation which holds for the populations of the SW energy levels defined by the SW model. By solving this differential equation with properly chosen initial conditions, a number of magnetization phenomena observed experimentally versus temperature, time, and external magnetic fields can be understood and described quantitatively. So, hysteresis loops, including those in high-frequency external magnetic fields, can be calculated within this model as a function of temperature, and demagnetization curves for arbitrary heating rates in different external magnetic fields can be simulated. In contrast to the difficulties encountered when treating the experimental data within more general stochastic models based on the Landau–Lifshitz–Gilbert equation, one can easily fit to a first approximation a wide set of data taken from the same sample within the extended SW model. The well known Henkel and Thamm–Hesse plots are reviewed and it is shown that by using these for plotting experimental data deviations from the ideal SW behavior and influences caused by relaxation can be detected. The plot recently proposed by Michele–Hesse–Bremers is shown not to be sensitive to relaxation influences and therefore reveals only the particle–particle interaction.

Item Type:Article
ID Code:5266
Deposited By:Prof. Alexey Ivanov
Deposited On:06 Aug 2009 11:04
Last Modified:06 Aug 2009 11:32

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