Magnetoresistive effect in graphene nanoribbon due to magnetic field induced band gap modulation

TL;DR

This paper theoretically demonstrates how a perpendicular magnetic field can modulate the bandgap in graphene nanoribbons, enabling magnetoresistance effects without ferromagnetic components, with implications for device applications.

Contribution

It reveals the bandgap modulation mechanism in armchair graphene nanoribbons under magnetic fields and explores the effects of temperature, bias, and edge roughness on magnetoresistance.

Findings

Large conductance modulation in AGNRs with Na=3p+1 under magnetic field.

MR ratio is high at optimal bias and decreases with temperature.

Edge roughness enhances magnetic sensitivity and MR ratio.

Abstract

The electronic properties of armchair graphene nanoribbons (AGNRs) can be significantly modified from semiconducting to metallic states, by applying a uniform perpendicular magnetic field (B-field). Here, we theoretically study the bandgap modulation induced by a perpendicular B-field. The applied B-field causes the lowest conduction subband and the top-most valence subband to move closer to one another to form the n=0 Landau level. We exploit this effect to realize a device relevant MR modulation. Unlike in conventional spin-valves, this intrinsic MR effect is realized without the use of any ferromagnetic leads. The AGNRs with number of dimers, Na=3p+1 [p=1,2,3,...] show the most promising behavior for MR applications, with large conductance modulation and hence, high MR ratio at the optimal source-drain bias. However, the MR is suppressed at higher temperature due to the spread of the Fermi function distribution. We also investigate the importance of the source-drain bias in optimizing the MR. Lastly, we show that edge roughness of AGNRs has the unexpected effect of improving the magnetic sensitivity of the device and thus increasing the MR ratio.