Permalloy-based carbon nanotube spin-valve

TL;DR

This paper demonstrates that Permalloy can effectively contact carbon nanotubes for spintronic applications, enabling sharp resistance switching and strong coupling suitable for spin-valve devices.

Contribution

It establishes Permalloy as a viable contact material for CNT spin-valves, showing tunable magnetization and strong coupling comparable to palladium.

Findings

Permalloy forms high-quality contacts with CNTs.

Permalloy exhibits sharp magnetization switching at cryogenic temperatures.

Permalloy contacts enable CNT quantum dot formation and spin-valve behavior.

Abstract

In this Letter we demonstrate that Permalloy (Py), a widely used Ni/Fe alloy, forms contacts to carbon nanotubes (CNTs) that meet the requirements for the injection and detection of spin-polarized currents in carbon-based spintronic devices. We establish the material quality and magnetization properties of Py strips in the shape of suitable electrical contacts and find a sharp magnetization switching tunable by geometry in the anisotropic magnetoresistance (AMR) of a single strip at cryogenic temperatures. In addition, we show that Py contacts couple strongly to CNTs, comparable to Pd contacts, thereby forming CNT quantum dots at low temperatures. These results form the basis for a Py-based CNT spin-valve exhibiting very sharp resistance switchings in the tunneling magnetoresistance, which directly correspond to the magnetization reversals in the individual contacts observed in AMR experiments.