Anomalous magnetoresistance in AuFe spin glass

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Abstract
Transverse magnetoresistance has been measured in AuFe polycrystals betweem 2.5 K and 300 K in magnetic fields up to 18 KG. For a sample with 2.9 at. % Fe (T0=16 K) the magnetoresistance at low temperature first increases with the field, peaks at around 1 KG and then decreases. The peak height decreases rapidly with increasing temperature. At temperatures above 6 K there is no measurable positive magnetoresistance even at 50 gauss. The negative component above 2 KG varies roughly as (Δρ/ρ) = −a(T) Bn with n=1.9±0.1. The amplitude a(T) saturates at low temperatures (2.5 K0. The alloys with higher Fe content (6.6, 10, 13, 18 at. % Fe) show that the magnetoresistance between 77 K and 300 K is negative but the field and the temperature dependence of (Δρ/ρ) changes significantly as one passes through the spin glass, mictomagnetic and inhomogeneous ferromagnetic regimes.