Magnetic viscosity in a nanocrystalline two phase composite with enhanced remanence

• Published in: Journal of magnetism and magnetic materials 2000, Vol.208 (1), p.1-12
• Main Authors: Billoni, O.V., Bordone, E.E., Urreta, S.E., Fabietti, L.M., Bertorello, H.R.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Fluctuation field; Irreversible magnetization; Magnetic aftereffects; Magnetic properties and materials; Magnetic viscosity; Nanocrystalline composites; Permanent magnets; Physics; Studies of specific magnetic materials
• ISSN: 0304-8853
• DOI: 10.1016/S0304-8853(99)00542-9

The intrinsic values of the magnetic viscosity and the fluctuation field in a two phase composite Nd 2Fe 14B+0.18 vol. αFe were investigated. The composite studied, with equiaxed and isotropically oriented grains had mean grain sizes favoring a strong exchange coupling between the phases. The relations between the intrinsic and the experimentally measured magnitudes are reviewed and the approximations discussed. For applied fields close to the coercivity, the time dependence of the magnetization is not well described by a simple logarithmic law. The intrinsic fluctuation field is found to increase when the reverse internal field increases in all the ranges investigated and two different regimes are identified. These different regimes are discussed considering the distributions of critical fields for nucleation of inverse domains in the hard phase, at hard–soft and hard–hard grain boundaries, respectively.