Coercivity of magnetic nanoparticles: a stochastic model

Chakraverty, Suvankar and Bandyopadhyay, Malay (2007) Coercivity of magnetic nanoparticles: a stochastic model. In: Journal of Physics: Condensed Matter, 19 (21). pp. 1-16.

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Abstract

The variation in magnetic properties with particle size for nanomagnetic particles at 300 K and 10 K has been explained with the help of nonequilibrium statistical mechanics. At room temperature a maximum in the coercivity curve is observed at a critical diameter, dc, so that two different regimes can be distinguished. This clearly indicates two different mechanisms of magnetization reversal as a function of particle size. Using Kramer's treatment, the increase in coercivity with an increase in particle size at room temperature in the single-domain region has been clarified. Beyond a certain critical particle size, a multidomain region is formed. Now we invoke supersymmetric quantum mechanics (SUSY QM) for these multi-domain region to explain the decrease in coercivity with an increase in particle size. The decrease in coercivity with an increase in particle size at very low temperature (10 K) is also explained with the help of our two-state model by invoking the concept of effective anisotropy. The variation in the saturation magnetization Ms and the remanence-to-saturation magnetization ratio, Mr Ms, with particle size are discussed in detail. The above results underscore the fact that at room temperature thermal effects dominate, whereas at low temperature (10 K) surface effects govern the magnetization reversal process. In this paper the effect of the magneto-crystalline anisotropic potential on the magnetization of non-interacting uniaxaial nanomagnetic particles is discussed in detail.

Item Type:	Journal Article
Publication:	Journal of Physics: Condensed Matter
Publisher:	IOP Publishing
Additional Information:	Copyright of this article belongs to IOP Publishing.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	09 Mar 2009 11:08
Last Modified:	19 Sep 2010 05:00
URI:	http://eprints.iisc.ac.in/id/eprint/18111

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