Growth and characterization of magnetic van der Waals films

In the recent past, magnetic, two-dimensional (2D), van der Waals (vdW) systems have become an exciting class of materials to study. On their own, these materials can give insights to low-dimensional spin behavior, but they also have the potential to be integrated into vdW heterostructures. Both areas are rich in scientific novelty and potential spintronics applications. Here we present the synthesis and characterization of 2D vdW magnets 1T-MnSe₂ and MnBi₂Se₄. The materials were grown by molecular beam epitaxy (MBE) and studied with various techniques including X-ray diffraction (XRD), spin-polarized scanning tunneling microscopy (SPSTM), and superconducting quantum interference device (SQUID). The XRD measurements show that highly crystalline MnBi₂Se₄ films can be grown consistently and SQUID measurements indicate a layered antiferromagnetic structure. This material also exhibits ferromagnetism in the monolayer limit with a Curie temperature near 10K. Monolayer 1T-MnSe₂ exhibits room-temperature ferromagnetism when analyzed with SQUID measurements. The magnetic signal from this material was also directly observed using SPSTM with a chromium tip.