Surface Termination-Enhanced Magnetism at Nickel Ferrite/2D Nanomaterial Interfaces: Implications for Spintronics

Engineeringof interfacial magnetic properties provides an extraedge in designing heterostructures with desired properties for spintronicsand spincaloritronics, without drastically changing the structureof the neighboring nonmagnetic material. Here, we report on the surfacetermination-enhanced magnetic properties of the ferrimagnetic insulator(FMI) nickel ferrite (NFO) with the inclusion of graphene (Gr) andmonolayer hexagonal boron nitride (hBN). Depth-dependent X-ray photoelectronspectroscopy (XPS) measurements reveal the presence of a layer ofadsorbed oxygen at the NFO/Gr and NFO/hBN interfaces. Magnetometryand transverse susceptibility measurements indicate that the inclusionof monolayer Gr increases the saturation magnetization (M (s)) by 40% and decreases the effective magnetic anisotropyby 50% across 5 K <= T <= 300 K. A similarbut less pronounced effect is observed for the inclusion of hBN. Densityfunctional theory calculations further indicate that the increasein M (S) due to the inclusion of Gr or hBNarises on oxygen-terminated NFO, as observed in XPS measurements.These results present ways for engineering strong interfacial magneticeffects in FMI/2D nanomaterial systems, controlling magnetism by surfacetermination, and developing advanced spinterfaces for applicationsin spincaloritronics and spin insulatronics.