Low-temperature specific heat study of amorphous and crystalline Co-Y alloys

Abstract

Low-temperature specific heats for ten amorphous and four crystalline Co-Y alloys have been measured in the temperature range 1.5-6 K. Both the linearly temperature-dependent specific heat coefficient gamma and the Debye temperature theta D in amorphous and crystalline phases exhibit a sharp increase at the composition where the ferromagnetism collapses. The enhancement in gamma is ascribed to the presence of the linearly temperature-dependent magnetic specific heat, which is often observed in the range where the ferromagnetism becomes unstable. The band-structure profile over a wide composition range is discussed in the light of recent band-structure calculations. The density of states at the Fermi level does not differ appreciably between the amorphous and crystalline phases and decreases gradually with increasing Y content. The internal magnetic field Hint was deduced from the 59Co nuclear specific heat coefficient. The authors found that Hint follows well a linear relationship with the magnetic moment per transition-metal atom.