Giant Tunneling Magnetoresistance in Spin-Filter van der Waals Heterostructures*

Magnetic multilayer devices that exploit magnetoresistance are the backbone of magnetic sensing and modern data storage technologies. However, van der Waals heterostructures with magnetic information storage and processing functionalities are still largely unexplored due to the lack of atomically thin 2D magnets. Recent breakthroughs in 2D magnetic materials offer a timely opportunity to explore these key functionalities in the atomically thin limit. Here we report novel multiple-spin-filter magnetic tunnel junctions (sf-MTJs) based on van der Waals (vdW) heterostructures in which atomically thin chromium triiodide (CrI₃) acts as a spin-filter tunnel barrier. We demonstrate drastically enhanced tunneling magnetoresistance with increasing CrI₃ layer thickness. Based on magnetic circular dichroism measurements, we attribute these effects to the intrinsic layer-by-layer antiferromagnetic ordering of atomically thin CrI₃. The realization of such vdW heterostructure sf-MTJs could thus stimulate the study of novel 2D magnetic interface phenomena and spintronics, such as spin current sources and magnetoresistive random-access memory (MRAM).