Principal Investigator Pablo Jarillo-Herrero
In this work, we introduce tunneling through layered insulators as a versatile probe of nanoscale magnetism. We fabricate van der Waals heterostructures of two graphite sheets separated by a magnetic CrI3 tunnel barrier. For magnetic tunnel junctions, the barrier height is lowered for electrons aligned with the magnetic layer, resulting in a direct dependence of the conductance across the junction on the magnetic ordering in the CrI3 barrier.
Layers of CrI3 align their spins perpendicular to the crystal, either up or down. By sweeping an applied magnetic field, we detect discrete steps in the junction conductance corresponding to individual layers in the CrI3 barrier flipping out-of- plane magnetization. For example, when the magnetic field is swept up past 1 T in the bilayer device, the spins in the two layers of CrI3 both align with the field, resulting in a 95% magnetoresistance.
Moreover, we can control the spin polarization of the output current with applied magnetic field, generating currents with up to 99% polarization. Thus, in addition to studying 2-D magnetic crystals using electrical readout of the magnetization, this result could also be applied to develop novel magnetic memory devices incorporating spin-orbit torques and other spintronic techniques.