Spin filtering effect in intrinsic 2D magnetic semiconductor Cr2Ge2Te6

TL;DR

This study investigates spin filtering in the 2D magnetic insulator Cr2Ge2Te6 within van der Waals heterostructures, revealing negative tunneling magnetoresistance indicative of minority spin conduction, advancing spintronic device research.

Contribution

It demonstrates spin-conserving tunneling and negative TMR in vdW heterostructures with Cr2Ge2Te6, providing new insights into spin-polarized transport in 2D magnetic insulators.

Findings

Negative junction magnetoresistance observed at low bias

Crossover from tunneling to Fowler-Nordheim tunneling with bias increase

Conduction band bottom in Cr2Ge2Te6 is minority spin

Abstract

All van der Waals (vdW) Fe3GeTe2/Cr2Ge2Te6/graphite magnetic heterojunctions have been fabricated via mechanical exfoliation and stacking, and their magnetotransport properties are studied in detail. At low bias voltages large negative junction magnetoresistances have been observed and are attributed to spin-conserving tunneling transport across the insulating Cr2Ge2Te6 layer. With increasing bias, a crossover to Fowler-Nordheim tunneling takes place. The negative sign of the tunneling magnetoresistance (TMR) suggests that the bottom of conduction band in Cr2Ge2Te6 belongs to minority spins, opposite to the findings of some first-principles calculations. This work shows that the vdW heterostructures based on 2D magnetic insulators are a valuable platform to gain further insight into spin polarized tunneling transport, which is the basis for pursuing high performance spintronic devices and a large variety of quantum phenomena.