Picture of magnetic graphene.
​Schematic representation of the graphene-ferromagnet (Cr2Ge2Te6) heterostructure. The brown, green blue and black balls correspond to Te, Ge, Cr and C atoms, respectively. The insets show the Dirac band structure of pristine graphene (left side) and ferromagnetic exchange splitting of graphene band in proximity with Cr2Ge2Te6 (right side). Illustration: Bogdan Karpiak

Engineering Magnetic Graphene in 2D Hybrid Devices

Researchers at Chalmers University of Technology have found that graphene can be made magnetic when placed in proximity with a layered insulating magnetic material in a van der Waals heterostructure. The findings were recently published in the scientific journal 2D Materials.
After graphene, various 2D materials of semiconducting and magnetic properties, among others, were discovered down to one-atom-thick layers. This opened plethora of opportunities for engineering heterostructures by combining the best of different 2D materials in one ultimate unit with different layers held together by weak van der Waals forces.

Here, Bogdan Karpiak, PhD student at the Quantum Device Physics Laboratory at the Department of Microtechnology and Nanoscience – MC2, assemble van der Waals heterostructures of the graphene and layered ferromagnetic insulator Cr2Ge2Te6. The choice of such a ferromagnet is motivated by its layered structure, insulating behavior, perpendicular magnetic anisotropy, and is expected to induce a magnetic exchange interaction in graphene in the heterostructure of the two materials. 

The researchers' measurements show an out-of-plane proximity-induced ferromagnetic exchange interaction in graphene, resulting in significant modification of the spin transport and dynamics in graphene. Furthermore, the observation of a larger lifetime for perpendicular spins in comparison to the in-plane counterpart suggests the creation of a proximity-induced anisotropic spin texture in graphene.

"This finding will open opportunities for the realization of proximity-induced magnetic interactions and spin-polarized filters in two-dimensional (2D) material heterostructure and can form the basic building blocks for future spintronics and topological quantum technologies", says Saroj Dash, associate professor and group leader at the Quantum Device Physics laboratory, and supervisor of the work. 

The article combines device fabrication and spin transport measurements in the Saroj Dash Group at Chalmers, magnetization measurements by Peter Svedlindh at Uppsala University, and theory calculation from the Jaroslav Fabian Group at University of Regensburg, Germany and the Stephan Roche Group at ICN2, Barcelona, Spain. This research at Chalmers is funded by the Graphene Flagship and the Swedish Research Council (VR).


Published: Thu 12 Dec 2019.