Positive Magnetoresistance in Concentrated γ-CuMn Alloys — An Evidence for Electron–Electron Interaction

Abstract

High-resolution transverse magnetoresistance (TMR) data in γ- Cu 100-x Mn x alloys (x = 36, 60, 73, 76 and 83) are presented till 7.5 T at 4.2, 20.5 and 63 K and longitudinal (LMR) magnetoresistance at 4.2 K. They show positive magnetoresistance till 7.5 T in the Mn-rich (x≥60) alloys while an overall negative one in the alloy with x = 36 at all temperatures. However, the data at 4.2 K in x=36 clearly demonstrate a positive magnetoresistance till 3 T which becomes negative at higher fields. The data for the Mn-rich alloys (x ≥ 60) at 4.2 and 20.5 K are well described by the electron–electron interaction effects (EEI) along with localisation and normal magnetoresistance. In the two regions of high (4 to 7.5 T) and low (0 to 1 T) fields, distinctly dominant contribution of EEI effects compared to that of localisation has been observed. For x = 36, an additional term due to the cluster-glass (CG) phase (=-β CG H2) has to be considered in explaining its overall negative magnetoresistance. However, the EEI/localisation effects have hardly any significant contribution at 63 K. The contribution of the combined EEI and localisation effects has been separated convincingly from the normal magnetoresistance (C N ) and the cluster-glass (β CG ) terms. The temperature dependence of the normal magnetoresistance follows the Kohler's rule while the cluster-glass term shows a behavior similar to those of the dilute spin glasses. Moreover, the present interpretation of magnetoresistance is found to be very much consistent with that of the electrical resistivity (ρ(T)).