Magnetic viscosity in a nanocrystalline two phase composite with enhanced remanence

O. V. BILLONI, E. E. BORDONE, S. E. URRETA, L.M. FABIETTI AND H.R. BERTORELLO

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

Año: 2000 p. 1 - 12

0304-8853

The intrinsic values of the magnetic viscosity and the fluctuation field in a two phase composite Nd2Fe14B+0.18 vol.aFe 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 foundto increase when the reverse internal field increases in all the ranges investigated and two di!erent regimes are identified.These di!erent regimes are discussed considering the distributions of critical fields for nucleation of inverse domains inthe hard phase, at hard-soft and hard-hard grain boundaries, respectively.