Unusually large negative magnetoresistance around 200 K in the alloys Gd_1-xLa_xMn₂Ge₂

Abstract

We report here the observation of large negative magnetoresistance (MR) at 200 K (for instance, about -5.5% for the application of a magnetic field of 70 kOe) in magnetic alloys, Gd1-xLaxMn2Ge2 (x = 0.07 and 0.08). There is a distinct sign reversal of MR, with a comparable magnitude, for x = 0.07 at 123 K thereby establishing the presence of temperature dependent magnetic structures. The observation of a large MR at temperatures as high as 200 K is uncommon among the bulk form of alloys.