Weak localisation in metallic glasses. I. Magnetoresistance

Abstract
The authors present magnetoresistance measurements at low temperature on a series of metallic glasses: Mg80Cu20, Cu50Lu50, Pd80Si20, Cu50Y50, Y80Si20, Cu57Zr43, CuYGd and CuLuGd. The magnetoresistance clearly exhibits three-dimensional localisation effects with a strong influence of the spin-orbit scattering: the magnetoresistance is negative for weak spin-orbit scattering (Mg80Cu20) and positive for strong spin-orbit scattering (Cu50Lu50, Pd80Si20), and changes from positive at low field to negative at high field for intermediate spin-orbit scattering (Cu50Y50, Cu57Zr43). The magnetoresistance curves can be accounted for by only localisation terms for most alloys and interaction effects are significant only for Y80Si20. An additional contribution from superconducting fluctuations is observed for the superconducting alloy Cu57Zr43. The analysis of the magnetoresistance yields the spin-orbit and inelastic scattering rates. The inelastic scattering rate of the alloys varies as T2 at high enough temperature and departs from T2 below about 5K. The measurements in a dilution refrigerator on Cu50Y50 and Y80Si20 have shown a variation as T1/2 below 1K. They discuss the possible origin of such a variation. They finally present measurements on Cu50Y50 and Y80Si20 doped with Gd. Surprisingly the addition of magnetic Gd impurities does not depress strongly the localisation effects, as would be expected from the existing theories.