Indirect Control of Buried CoB Spin Textures via C$_{60}$-Induced Modification of Ir Spin-Orbit Coupling

Abstract

Understanding how organic materials modulate magnetic structure is a central challenge in organic spintronics. Here, we demonstrate that C$_{60}$ molecular films exert a pronounced and quantifiable influence on the buried magnetic spin texture in Pt/CoB/Ir based multilayer systems hosting interfacial Dzyaloshinskii-Moriya interaction (iDMI). Using Lorentz transmission electron microscopy, the magnetic domain behaviour in field-free and in-situ field environments is measured. In Fresnel mode, we reveal a reduction in magnetic domain periodicity upon C$_{60}$ deposition. Then, using pixelated 4D-STEM differential phase contrast mode, we establish that this modification arises from a substantial enhancement of effective magnetic anisotropy and interfacial DMI strength. Coupled with bulk magnetometry and micromagnetic simulations, we propose a mechanism based on spin-orbit coupling at the C$_{60}$/Ir interface which modifies the iDMI and drives a contraction of spin texture density throughout the multilayer stack. These findings extend the impact of organic molecular capping films as effective and accessible routes for engineering spin textures to buried magnetic multilayer systems, with direct implications for the design of next-generation spintronic and neuromorphic devices.