Nonsaturating magnetoresistance of inhomogeneous conductors: Comparison of experiment and simulation

Abstract

The silver chalcogenides provide a striking example of the benefits of imperfection. Nanothreads of excess silver cause distortions in the current flow that yield a linear and nonsaturating transverse magnetoresistance ͑MR͒. Associated with the large and positive MR is a negative longitudinal MR. The longitudinal MR only occurs in the three-dimensional limit and thereby permits the determination of a characteristic length scale set by the spatial inhomogeneity. We find that this fundamental inhomogeneity length can be as large as 10 m. Systematic measurements of the diagonal and off-diagonal components of the resistivity tensor in various sample geometries show clear evidence of the distorted current paths posited in theoretical simulations. We use a random-resistor network model to fit the linear MR, and expand it from two to three dimensions to depict current distortions in the third ͑thickness͒ dimension. When compared directly to experiments on Ag 2±␦ Se and Ag 2±␦ Te, in magnetic fields up to 55 T, the model identifies conductivity fluctuations due to macroscopic inhomogeneities as the underlying physical mechanism. It also accounts reasonably quantitatively for the various components of the resistivity tensor observed in the experiments.

Особенности транспортных свойств соединения Lu-=SUB=-0.1-=/SUB=-Bi-=SUB=-1.9-=/SUB=-Te-=SUB=-3-=/SUB=-

“…Поле кроссовера B c уменьшалось при понижении температуры, т. е. линей-ный вклад в общую зависимость MR(B) постепенно возрастал. Линейное положительное магнитосопротивление в металлах и полупроводниках может быть обусловлено несколькими механизмами [10][11][12][13]. Один из механизмов развит для структурно неоднородных и неупорядочен-ных полупроводников [12,13].…”

Transition from positive to negative magnetoresistance induced by a constriction in semiconductor nanowire

“…6 The explanation of the non-saturating properties of MR can be based on the large spatial fluctuations in the conductivity of the narrow-gap semiconductors, due to the inhomogeneous distribution of silver ions. 7,8 It has been also shown that the large positive MR is induced by the quasi-neutrality breaking of the space-charge effect in Si. 9 The large positive MR has been also reported by Schoonus et al in Boron-doped Si-SiO 2 -Al structures.…”

Magnetoresistance of doped silicon

“…Several mechanisms have been suggested to explain this behavior from geometrical [22], classical [23][24][25], quantum [26,27], and effective medium [28,29] perspectives.…”