Electrical Detection of a Metamagnetic Transition in a van der Waals Magnetic Insulator*

The operation of modern magnetic memories relies on the interplay of magnetism and conductivity in ferromagnetic metals. In theory, higher performance is possible for tunneling through insulating magnets, but the requirement of ultrathin films has limited this concept. Here, we measure tunneling through atomically thin crystals of the magnetic insulator CrI₃ prepared by mechanical exfoliation. Owing to the weak antiferromagnetic interlayer coupling in CrI₃, we can orient the magnetization in adjacent layers to be either parallel or antiparallel using an external magnetic field. When we switch the interlayer magnetization alignment, we observe a 100%, 300%, and 550% conductance change for bilayer, trilayer, and tetralayer CrI₃ barriers, respectively. We further observe evidence of collective modes in tunneling bias spectroscopy, establishing vertical tunneling as a spectroscopic probe for atomically thin magnetic materials.