Monte Carlo simulations of interaction effects on magnetic viscosity in ferromagnetic granular media

Issue title: Proceedings of the tenth International Symposium on Applied Electromagnetics and Mechanics ISEM-Tokyo

Article type: Research Article

Authors: Verdes, C.G.^{a; *} | Diaz, B.R.^d | Chantrell, R.W.^b | Thompson, S.^d | Stancu, Al.^c

Affiliations: [a] Magnetic Materials Research Group, Center for Materials Science, University of Central Lancashire, Preston, PR1 2HE, UK | [b] Department of Physics, University of Durham, Durham, DH1 3LE, UK | [c] "Al. I. Cuza" University, Iasi, Romania | [d] Department of Physics, University of York, York, YO10 5DD, UK

Correspondence: [*] Corresponding author: C.G. Verdes, Fax: 0191 3743749; E-mail: [email protected]

Abstract: A Monte Carlo time and temperature dependent model was developed to simulate magnetization processes in fine ferromagnetic particle media. The model uses a combination between a time dependent Stoner-Wohlfarth model and a standard Metropolis algorithm to find the magnetization of single-domain particle systems. Both magnetostatic and exchange interactions are introduced explicitly. Variation of magnetic viscosity with interactions and temperature is studied. Results show that viscosity exhibits a maximum around coercive field. The value of this maximum is closely related to the strength and the origin of interactions as well as to temperature. Dipolar interactions decrease the viscosity and broaden the viscosity vs. field curve, while exchange interactions lead to an increase in viscosity around coercive field. An increase in temperature up to the critical temperature for the superparamagnetic behavior leads to an increase in viscosity. Further increase of temperature produces a decrease in viscosity.

DOI: 10.3233/JAE-2002-330

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 13, no. 1-4, pp. 251-256, 2002