Weak localisation in metallic glasses. I. Magnetoresistance

The authors present magnetoresistance measurements at low temperature on a series of metallic glasses: Mg 80 Cu 20 , Cu 50 Lu 50 , Pd 80 Si 20 , Cu 50 Y 50 , Y 80 Si 20 , Cu 57 Zr 43 , 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 (Mg 80 Cu 20 ) and positive for strong spin-orbit scattering (Cu 50 Lu 50 , Pd 80 Si 20 ), and changes from positive at low field to negative at high field for intermediate spin-orbit scattering (Cu 50 Y 50 , Cu 57 Zr 43 ). The magnetoresistance curves can be accounted for by only localisation terms for most alloys and interaction effects are significant only for Y 80 Si 20 . An additional contribution from superconducting fluctuations is observed for the superconducting alloy Cu 57 Zr 43 . The analysis of the magnetoresistance yields the spin-orbit and inelastic scattering rates. The inelastic scattering rate of the alloys varies as T 2 at high enough temperature and departs from T 2 below about 5K. The measurements in a dilution refrigerator on Cu 50 Y 50 and Y 80 Si 20 have shown a variation as T 1/2 below 1K. They discuss the possible origin of such a variation. They finally present measurements on Cu 50 Y 50 and Y 80 Si 20 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.