Magnetic and anomalous magnetic viscosity in the bulk amorphous ferromagnet and partially amorphous ferromagnet

Temperature dependence of the coercivity in Nd60Fe30−xCoxAl10, x=0 or 10, and Pr58Fe24Al18 bulk amorphous ferromagnets

“…The observation of the similarity of the magnetic and microstructural length scales has also been made by Schneider et al [32], based on small angle neutron scattering and transmission electron microscopy investigations. Length scales deduced from determination of the activation volume, from magnetic viscosity experiments, also support this view [22]. This is not surprising, as the observed magnetic behaviour is a manifestation of the same underlying thermal activation processes.…”

“…Each sample was in the form of a rod, about 6 mm long and 2 mm in diameter. The alloy samples were examined using X-ray powder diffraction (XRD) with Cu-K a radiation, which showed each sample to be amorphous (see [22] for a typical XRD pattern), with only a trace ð o1%Þ of crystallinity evident.…”

Application of the Stoner–Wohlfarth model with interaction for the determination of the saturation magnetisation, anisotropy field, and mean field interaction in bulk amorphous ferromagnets

“…The rods were prepared by argon-arc melting and suction casting into a split copper mould. The alloy samples were examined using X-ray powder diffraction (XRD) with Cu À K a radiation, which showed each sample to be amorphous (see [22] for a typical XRD pattern), with only a trace ( o 1%) of crystallinity evident.…”

“…Whilst simple laboratory XRD was used to confirm the amorphous nature of the specimens under study here, and the XRD pattern of the type shown in [22] is generally accepted as confirming the material as being amorphous, it should be recognised that laboratory XRD has limitations when it comes to probing structural detail that may have a nanometre length scale. Higher resolution techniques such as those using synchrotron radiation are superior, and when applied to bulk amorphous Nd 60 Fe 30 Al 10 may reveal small entities or nanocrystalline clusters of order 1.2 nm in diameter embedded in an amorphous matrix [13].…”

“…These are both of a similar dimension to the length scale of the nanocrystalline clusters embedded in the amorphous matrix. Magnetic viscosity experiments, from which the activation volume has been deduced, give values for an activation diameter or length of % 20 nm [46,47]. At one level, if a large random anisotropy is responsible for coercivity, a length scale much less than 10 nm might be expected, as the highanisotropy regime involves only a few spins.…”