(198l) Proximal Interactions in Graphene-Magnetic Nanoparticle Interfacial Composites

The single layer honeycomb carbon lattice of graphene is responsible for many of its exceptional properties such as high electron mobility, flexibility, and thermal conductivity. This has resulted in intense exploration of graphene for electronic, energy, and biosensing applications. However, the structure of graphene does not yield intrinsic magnetic order that would be desirable for potential magneto-electronic and spintronic applications. Most investigations directed toward generation of magnetism in graphene either demonstrate short range magnetism or are accompanied by disruption of its inherent properties. A recent study successfully induced long range magnetism in graphene while preserving its pristine attributes by harnessing the sensitivity of graphene electronic orbitals to proximal magnetic materials [1]. Drawing inspiration from this approach, this research examines the potential of superparamagnetic iron oxide nanoparticles (SPIONs) for proximity induced magnetism. The use of SPIONs had the potential additional advantage to locally control magnetization by directed self assembly of SPIONs. Further, the use of nanoscale materials may enable quantum level interactions. These graphene-SPION composites could thus enable emergent proximal interactions, perhaps with the ability to locally control magnetism.

Here, we describe composites that are assembled by transferring graphene to a silicon dioxide substrate onto which SPIONs have been deposited. Deposition techniques including spin coating [2] and the Langmuir Blodgett trough method [3] were utilized to produce scalable and controlled self assembly of SPIONs with different levels of ordering and surface densities. Atomic (AFM) and Magnetic (MFM) Force Microscopy were used to evaluate the topography of the composite throughout the assembly process. Subsequently, potential for perturbations in the inherent structural and electronic properties of graphene after transfer onto SPION-coated substrates was evaluated using Raman spectroscopy and resistivity measurements, respectively. To determine if magnetism was induced in the graphene structure, Hall and Quantum Hall effect measurements were conducted. Primary measurements on random, low density SPION arrays showed that composites maintained native graphene characteristics. High density arrays with ordering are being evaluated for comparison. Ultimately, this research will elucidate the potential to induce localized and global coupling of graphene to the nanomaterials in immediate vicinity.

[1] Z. Wang, C. Tang, R. Sachs, Y. Barlas, J. Shi, Proximity-induced ferromagnetism in graphene revealed by the anomalous Hall effect, Phys Rev Lett, 114 (2015) 016603.

[2] M. Benitez, D Mishra, P Szary, G. Badini Confalonieri, M. Feyen, A. Lu, L. Agudo, G. Eggeler, O. Petracic, H. Zabel, Structural and magnetic characterization of self-assembled iron oxide nanoparticle arrays, J. Phys.: Condens. Matter 23 (2011) 126003.

[3] Q. Guo, X. Teng, S. Rahman, H. Yang, Patterned Langmuir-Blodgett Films of Monodisperse Nanoparticles of Iron Oxide Using Soft Lithography, J. AM. CHEM. SOC., 125 (2003), 630-631.