Magnetic, electronic, and electron-transport properties of amorphous (Co0.85B0.15)100-xXx (X=B, Al, Si, and V) alloys

The magnetic state in amorphous (Co0.85B0.15)100-xXx (X=B, Al, Si, and V) prepared by liquid quenching has been studied through the measurements of the saturation magnetization at 4.2 K, the Curie temperature, and the spin-wave stiffness constant. The electronic structure was investigated by measuring the low-temperature specific heats and ultraviolet-photoemission-spectroscopy valence-band spectra. Combining the previously reported data on amorphous (Co0.9Zr0.1)100-xXx (X=Al, Si, Cu, Ge, and Zr) alloys, we could show that the linearly temperature-dependent specific-heat coefficient γexpt in these ferromagnetic amorphous alloys reflects well the density of states N(EF) at the Fermi level, provided that the spin-wave stiffness constant is above about 150 meV A2. The electron-transport properties have been discussed in detail only for those whose γexpt offers reliable information on N(EF). The participation of weak-localization effects has been concluded from the following: (1) the coefficient ξ of logarithmic temperature dependence of resistivity at low temperatures increases while TCR, the temperature coefficient of resistivity defined as (1/ρ)(dρ/dT), near 300 K decreases with increasing resistivity and (2) amorphous alloys with the largest values of ξ are always found near the high-resistivity limiting curve on the ρ-γ diagram. © 1993 The American Physical Society.