Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling

TLDR

Magnetic insulators, especially layered metal halides, are promising for spintronic and topological devices but require new characterization methods to unlock their ultrathin insulating multiferroic, spin liquid, and ferromagnetic potential. We investigate temperature‑ and field‑dependent tunneling through layered CrI3 to probe its magnetic properties. Vertical tunneling measurements of CrI3 layers electrically detect the magnetic ground state, inter‑layer coupling, and a field‑induced metamagnetic transition. The field‑induced metamagnetic transition yields magnetoresistances of 95 %, 300 %, and 550 % in bilayer, trilayer, and tetralayer CrI3, while inelastic tunneling spectra reveal a rich magnon spectrum, establishing vertical tunneling as a versatile probe of magnetism in atomically thin insulators.

Abstract

Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises ultrathin insulating multiferroics, spin liquids, and ferromagnets, but new characterization methods are required to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI3 as a function of temperature and applied magnetic field. We electrically detect the magnetic ground state and inter-layer coupling and observe a field-induced metamagnetic transition. The metamagnetic transition results in magnetoresistances of 95%, 300%, and 550% for bilayer, trilayer, and tetralayer CrI3 barriers, respectively. We further measure inelastic tunneling spectra for our junctions, unveiling a rich spectrum of collective magnetic excitations (magnons) in CrI3. Our results establish vertical tunneling as a versatile probe of magnetism in atomically thin insulators.