C-based materials play a significant role in the development of next-generation semiconductor electronics. Recent developments in combining ferromagnetic materials and amorphous C have resulted in interesting magneto-electronic and magneto-optical (MO) properties, and findings suggest the potential technological spintronic applications of C-based thin films. Interfacial hybridization between sp² C atoms and the d-orbit of transition metal atoms can strongly influence the physical properties of such materials. In addition, controlling the magnetic-related phenomena of a medium with the help of electric fields is an emerging and rapidly developing research direction in modern magnetism. However, the voltage (V) control of magnetic-related phenomena in C based magnetic hybrid structures remains less explored. Since variations in spin-polarized density of states (DOSs) may be related to variations in MO effects, a fundamental question remains: Does application of a V affect the MO effect in magnetic Co/C heterostructures?

In this work, electrical manipulation of the magneto-optical properties of a Co/C heterostructure is demonstrated via reversible V-dependent magnetic circular dichroism (MCD) measurements to provide information on its spin-polarized DOSs. Combination of the complex impedance, x-ray absorption, and Raman results also indicated that the MCD changes observed could be attributed to charge accumulation in defects near the Co/C interface. The θ-dependent ∆MCD values obtained under an applied V confirmed that reversible variations in C–Co hybridization play an important role in the observed phenomena. The results are of considerable interest in the areas of electrically controlled MO properties and C-based spintronics.