Current jets, disorder, and linear magnetoresistance in the silver chalcogenides

The inhomogeneous distribution of excess or deficient silver atoms lies behind the large and linear transverse magnetoresistance displayed by Ag2 +/-delta Se and Ag2 +/-delta Te, introducing spatial conductivity fluctuations with length scales independent of the cyclotron radius. We report a negative, nonsaturating longitudinal magnetoresistance up to at least 60 T, which becomes most negative where the bands cross and the effect of conductivity fluctuations is most acute. Thinning samples down to 10 mu m suppresses the negative response, revealing the essential length scale in the problem and paving the way for designer magnetoresistive devices.