Magnetoresistance in microwave synthesized Ag2+delta Se (0.0 <=delta <= 0.2) - art. no. 212405

Compositional variation of magnetoresistance (MR) ratio with silver excess stoichiometry in Ag2+deltaSe samples has been studied employing a synthetic approach to prepare instantly a series of bulk silver selenide compounds u sing microwave energy. Bulk density >99% is achieved in situ, by means of v olumetric heating/sintering in less than 10 min, which makes this process u nique compared to other chemical and nonchemical approaches. We observe a s ystematic decrease in metal-insulator transition with increasing Ag. Magnet oresistance ratio observed in transverse geometry is 145%, greater than the longitudinal geometry (70%). This series shows linear dependence of MR wit h higher fields (3 <H<16 T) with no saturation of MR ratio even at 16 T in transverse mode. However, a distinct saturation effect was noticed in almos t all the compositions for magnetic field above 13 T in longitudinal mode. Electron probe microanalysis shows an elemental-rich selenium phase for del ta =0.05 composition which accounts for low resistivity, large magnetoresis tance ratio and unsymmetrical MR curves when field is applied in both the d irections. This is attributed to the charge density fluctuations in chemica lly inhomogeneous systems. At 300 K, MR ratios of 30 and 59 % for delta =0. 2, in longitudinal and transverse mode is observed, respectively.