Transformation of spin information into large electrical signals via carbon nanotubes

TL;DR

This paper demonstrates a significant advancement in spintronics by achieving a 61% magnetoresistance in carbon nanotube-based devices, overcoming previous limitations of low electrical signal transformation from spin information.

Contribution

The study introduces a novel spintronic device using carbon nanotubes that significantly enhances magnetoresistance, leveraging long spin lifetimes and optimized interfaces.

Findings

Achieved 61% magnetoresistance at 5 K in nanotube devices.

Long spin lifetime in nanotubes due to low spin-orbit coupling.

Interfacial properties supported by density functional theory calculations.

Abstract

Spin electronics (spintronics) exploits the magnetic nature of the electron, and is commercially exploited in the spin valves of disc-drive read heads. There is currently widespread interest in using industrially relevant semiconductors in new types of spintronic devices based on the manipulation of spins injected into a semiconducting channel between a spin-polarized source and drain. However, the transformation of spin information into large electrical signals is limited by spin relaxation such that the magnetoresistive signals are below 1%. We overcome this long standing problem in spintronics by demonstrating large magnetoresistance effects of 61% at 5 K in devices where the non-magnetic channel is a multiwall carbon nanotube that spans a 1.5 micron gap between epitaxial electrodes of the highly spin polarized manganite La0.7Sr0.3MnO3. This improvement arises because the spin lifetime in nanotubes is long due the small spin-orbit coupling of carbon, because the high nanotube Fermi velocity permits the carrier dwell time to not significantly exceed this spin lifetime, because the manganite remains highly spin polarized up to the manganite-nanotube interface, and because the interfacial barrier is of an appropriate height. We support these latter statements regarding the interface using density functional theory calculations. The success of our experiments with such chemically and geometrically different materials should inspire adventure in materials selection for some future spintronics