The peak in anomalous magnetic viscosity

• Published in: Journal of magnetism and magnetic materials Vol. 360; pp. 118 - 125
• Main Authors: COLLOCOTT, S. J, WATTERSON, P. A, TAN, X. H, XU, H
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01.06.2014
• Subjects: Alloys; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Ferromagnetism; Fluctuation; Magnetic aftereffects; Magnetic properties and materials; Magnetism; Magnetization; Mathematical models; Origins; Physics; Viscosity; Preisach model; Fluctuations; Magnetization; Ferromagnetic materials; Amorphous alloy; Iron alloys; Anomalous magnetic viscosity; Neodymium alloys; Time dependence; Bulk amorphous ferromagnet; Coercive force; Rare earth alloys; Chemical composition; Magnetic aftereffect; Transition element alloys
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2014.02.046

Anomalous magnetic viscosity, where the magnetization as a function of time exhibits non-monotonic behaviour, being seen to increase, reach a peak, and then decrease, is observed on recoil lines in bulk amorphous ferromagnets, for certain magnetic prehistories. A simple geometrical approach based on the motion of the state line on the Preisach plane gives a theoretical framework for interpreting nonmonotonic behaviour and explains the origin of the peak. This approach gives an expression for the time taken to reach the peak as a function of the applied (or holding) field. The theory is applied to experimental data for bulk amorphous ferromagnet alloys of composition Nd sub(60-x)Fe sub(30)Al sub(10)Dy sub(x), x = 0,1, 2, 3 and 4, and it gives a reasonable description of the observed behaviour. The role played by other key magnetic parameters, such as the intrinsic coercivity and fluctuation field, is also discussed. When the non-monotonic behaviour of the magnetization of a number of alloys is viewed in the context of the model, features of universal behaviour emerge, that are independent of alloy composition.