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Proceedings Paper

Non-equilibrium magnetism of nanoparticles revealed in static and radiofrequency measurements
Author(s): M. A. Chuev; N. P. Aksenova; P. G. Medvedev; A. M. Afanas'ev
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Paper Abstract

Magnetic relaxation effects revealed in Moessbauer spectra and magnetization measurements of nanoparticles are discussed in the framework of a general model for magnetic dynamics of ensemble of single-domain particles. The phenomenological model is based on a generalization of the well-known Stoner-Wohlfarth model within more accurate description of relaxation processes and corresponding time-dependent hyperfine interactions in the magnetic system. This model allows one to treat numerically both Moessbauer spectra in radiofrequency magnetic field and magnetization curves in alternative low-frequency magnetic field as well as temperature demagnetization FC and ZFC curves in a self-consistent way within the same set of physical parameters inherent to the system studied. Besides that, a number of qualitative effects can be explained or predicted within the approach, which include interaction effects, relaxation-stimulated resonances in Moessbauer spectra under radiofrequency field excitation, specific shapes of Moessbauer spectra within precession of particle's uniform magnetization, and asymptotic high-temperature magnetization and susceptibility behavior different from the classical Langevin's high-temperature limit for ideal superparamagnetic particles. Corrections to the above-mentioned effects within more general models based on the Landau-Lifshitz-Gilbert or Braun kinetic equations are also discussed.

Paper Details

Date Published: 29 April 2008
PDF: 11 pages
Proc. SPIE 7025, Micro- and Nanoelectronics 2007, 70250S (29 April 2008); doi: 10.1117/12.802418
Show Author Affiliations
M. A. Chuev, Institute of Physics and Technology (Russia)
N. P. Aksenova, Institute of Physics and Technology (Russia)
P. G. Medvedev, Institute of Physics and Technology (Russia)
A. M. Afanas'ev, Institute of Physics and Technology (Russia)

Published in SPIE Proceedings Vol. 7025:
Micro- and Nanoelectronics 2007
Kamil A. Valiev; Alexander A. Orlikovsky, Editor(s)

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