Van der Waals spin valves

TL;DR

This paper introduces a new type of spin valve using 2D non-magnetic conductors like graphene between ferromagnetic insulators, showing how magnetic orientation controls electronic conductivity.

Contribution

It demonstrates the concept of van der Waals spin valves with theoretical modeling and DFT calculations, revealing magnetic configuration-dependent band gap opening in graphene bilayers.

Findings

Band gap opens in antiparallel magnetic configuration

Conductivity varies with magnetic orientation

DFT confirms model predictions

Abstract

We propose spin valves where a 2D non-magnetic conductor is intercalated between two ferromagnetic insulating layers. In this setup, the relative orientation of the magnetizations of the insulating layers can have a strong impact on the in-plane conductivity of the 2D conductor. We first show this for a graphene bilayer, described with a tight-binding model, placed between two ferromagnetic insulators. In the anti-parallel configuration, a band gap opens at the Dirac point, whereas in the parallel configuration, the graphene bilayer remains conducting. We then compute the electronic structure of graphene bilayer placed between two monolayers of the ferromagnetic insulator CrI$_3$, using density functional theory. Consistent with the model, we find that a gap opens at the Dirac point only in the antiparallel configuration.