Stabilizing Ferromagnetic Interfaces in Perovskite/Co Heterostructures Using 2D Interlayers

Abstract

Chirality-induced spin selectivity has recently attracted attention for applications in spintronic devices. Chiral perovskites (PVSK), with left- or right-handed molecular configurations, have been shown to modulate the optical, magnetic, and electrical properties of such devices. Since this effect is highly sensitive to interfacial environments, controlling spin selectivity at different material interfaces is of particular importance. In this study, we investigate the interfacial interactions between chiral PVSK and ferromagnetic cobalt (Co) layers. Elemental composition and chemical states of the heterostructures were analyzed to assess magnetic and chemical stability. Introducing two-dimensional (2D) materials between PVSK and Co was found to promote the formation of continuous PVSK films and improve interfacial stability. Specifically, we inserted hexagonal boron nitride (hBN) and graphene (Gr) layers between PVSK and Co to evaluate their protective effects. Direct PVSK/Co contact results in severe magnetic degradation, yielding an average non-ferromagnetic Co thickness of 3 ± 1 nm. In contrast, Gr provides the strongest protection, suppressing Co degradation to 0.6 ± 0.5 nm and minimizing perovskite diffusion into the ferromagnetic layer. X-ray photoelectron spectroscopy (XPS) further confirms the superior protective role of Gr, showing a dominant metallic Co signal at the interface.

Keywords: Interface, Chiral Perovskite, Ferromagnetism, Redox reaction, Thin film