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Reversible processes and magnetic viscosity of nanocrystalline permanent magnets

1998; American Institute of Physics; Volume: 83; Issue: 11 Linguagem: Inglês

10.1063/1.367784

1520-8850

D.R. Cornejo, Valquı́ria Villas-Boas, F.P. Missell,

Magnetic and transport properties of perovskites and related materials

The accurate determination of the magnetic viscosity parameter Sv requires the calculation of a new parameter η=(∂Mrev/∂Mirr)Hi which describes the dependence of reversible magnetization on irreversible magnetization. Measurements of the magnetic viscosity were performed at 300 K on the major demagnetization curves of two different nanocrystalline permanent magnetic materials: (i) melt-spun and flash-annealed Pr4Fe78B18 and (ii) mechanically alloyed and heat-treated Sm18Fe33Co49. We show that η is proportional to the intrinsic reversible susceptibility χrevi, in good agreement with predictions of the moving Preisach model. Measurements of the reversible susceptibility were made in order to determine η. Experimental values of η are positive on the major demagnetization curve in both materials, resulting in substantial corrections to Sv near Hc.