Band-gap tuning and linear magnetoresistance in the silver chalcogenides

Optimally doped silver selenide and silver telluride exhibit linear positive magnetoresistance over decades in magnetic field and on a scale comparable to the colossal magnetoresistance compounds. We use hydrostatic pressure to smoothly alter the band structure of Ag-rich and Ag-deficient samples of semiconducting Ag2+/-delta of fixed stoichiometry and disorder. We find that the magnetoresistance spikes and the linear field dependence emerges when the bands cross and the Hall coefficient changes sign.