Megagauss sensors

Abstract

Magnetic fields change the way that electrons move through solids. The nature of these changes reveals information about the electronic structure of a material and, in auspicious circumstances, can be harnessed for applications. The silver chalcogenides, Ag2Se and Ag2Te, are non-magnetic materials, but their electrical resistance can be made very sensitive to magnetic field by adding small amounts--just 1 part in 10,000--of excess silver. Here we show that the resistance of Ag2Se displays a large, nearly linear increase with applied magnetic field without saturation to the highest fields available, 600,000 gauss, more than a million times the Earth's magnetic field. These characteristics of large (thousands of per cent) and near-linear response over a large field range make the silver chalcogenides attractive as magnetic-field sensors, especially in physically tiny megagauss (10(6) G) pulsed magnets where large fields have been produced but accurate calibration has proved elusive. High-field studies at low temperatures reveal both oscillations in the magnetoresistance and a universal scaling form that point to a quantum origin for this material's unprecedented behaviour.

Topological Insulator Materials

“…Ag 2 Te has been known to be a material presenting large, linear-in-B magnetoresistance over an exceedingly wide magnetic-field range, 132) and it has been proposed that this unusual property may be associated with its 3D-TI nature. 133) ARPES measurements of this material have not been reported, but Aharonov-Bohm (AB) oscillations have been observed in nanowires of Ag 2 Te.…”

Nonsaturating magnetoresistance of inhomogeneous conductors: Comparison of experiment and simulation

“…Moreover, the curves at different temperatures do not coincide with the scaling form ⌬R / R = f͑ ͒, but are shifted by a multiplicative factor that depends on temperature. 16 The PL model is able to account for the linearity at low fields by showing that the linear, transverse MR of a heavily inhomogeneous semiconductor crosses over to quadratic behavior at a field set by the inverse of the mobility distribution width ⌬ , rather than the average mobility ͗ ͘, provided that ⌬ / ͗ ͘ Ͼ 1. In addition, the character of the mobility distribution determines the magnitude of the linear response: at sufficiently large fields, ⌬R / R ϰ⌬ H for strongly disordered semiconductors with ⌬ / ͗ ͘ Ͼ 1.…”

“…They exhibit negligible physical magnetoresistance, 11 as predicted from conventional theories. By contrast, minute amounts of excess Ag or Te/ Se-at levels as small as 1 part in 10 000-lead to a huge and linear magnetoresistance over a broad temperature range, with no sign of saturation up to 60 T. [12][13][14][15][16][17] In particular, the unusual linearity extends deep into the low-field regime with H Ӷ 1/ , where is the typical mobility of the material. Such behavior shows no resemblance to conventional semiconductors, where the magnetoresistance grows quadratically with field and reaches saturation at fields typically of order 1 T. Therefore, it has been argued that the observed magnetoresistance must be caused by the inhomogeneous distribution of excess or deficient silver ions.…”

Current Jets, Disorder, and Linear Magnetoresistance in the Silver Chalcogenides

“…The unusual linear dependence on magnetic field down to 100 G indicates a particularly long length scale associated with the underlying physics, while, at high field, a nonsaturating response up to at least 0.5 MG exceeds by a factor of 50 to 100 the expected cutoff where the product of the cyclotron frequency and the scattering rate ! 1 [9]. This remarkably robust linear magnetoresistive response makes the silver chalcogenides promising candidates for high field sensors.…”