Electronic states and localized magnetic moments and their interactions were studied in amorphous and crystalline Zr40Cu60-xFex alloys for 0≤x≤12. Electrical resistivity, magnetic susceptibility, and high-field magnetization measurements were performed. In the dilute crystalline alloys Curie-Weiss behavior is seen in the susceptibility and is associated with localized moments (μeff3μB) on the iron atoms. At higher iron concentrations ferromagnetism is observed. Curie-Weiss behavior also is seen in the susceptibility of the dilute (0<x≤6) amorphous alloys; however, for these alloys the dependence on Fe concentration appears complex and the effective moments on the iron atoms are very small (μeff0.7μB). There is some evidence that the local environment of the Fe atoms is important and may depend sensitively on the quench rate used in making the samples or, perhaps, on room-temperature ageing effects in the samples. The dilute amorphous alloys exhibit a negative dρd T from 1.4 to 300 K. This is not to be associated with Kondo spin-flip scattering but it is consistent with several other mechanisms including localized-spin-fluctuation scattering, s-d scattering in a nonmagnetic model, scattering from tunneling states in the amorphous alloy, or quasi-liquidmetal-pseudopotential scattering. A recent theory due to Nagel and Tauc on the nearly-free-electron approach to metallic glass alloys is shown to be consistent with this last idea and also is used to account for other features exhibited by the amorphous Zr-Cu system. In the concentrated (x>6) amorphous alloys, resistance maxima and magnetic hysteresis are seen at low temperatures. For x=12 a random ferromagnetic state develops with T0=30 K, which is some five times smaller than T0 for the corresponding crystalline alloy. The saturation moment in the amorphous alloy is also considerably smaller than in the crystalline case. This behavior is similar to other systems in which the crystalline-to-amorphous transition greatly weakens the magnetism.
ASJC Scopus subject areas
- Condensed Matter Physics