Theoretical Study of Spintronics Devices Based on Two-Dimensional Materials

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A first-principles study was done to look at the effect of spin-orbit coupling (SOC) on the interface between graphene (Gr) and nickel (Ni). Due to SOC, when Ni atoms were far from the interface, they were magnetized in a parallel direction to the interface. As they move toward the interface, they begin to rotate in a direction perpendicular to the interface until they have full perpendicular magnetization at the interface. This rotation is caused by the fact that hybridization with Gr reduces the in-plane orbital moment and makes the out-of-plane orbital moment stronger at the interface. This result was also applied to the hexagonal Boron Nitride (hBN)/Ni interface. Further, it was confirmed that this effect does not affect the controllable Dirac cone of graphene in the proposed Ni/Gr/Ni as well as Ni/hBN-Gr-hBN/Ni device, showing the effectiveness of controlling in-plane spin-current on Gr for the spin-valve device.Parallelly, we found a spin-flipping mechanism that can be initiated on the induced magnetic moment of C atoms in Gr/Ni when it hybridizes with a metal atom of the metal complex and a mechanical disturbance is made to the metal complex. This spin-flipping happens because the density of states of C atoms in the spin-majority channel near Fermi energy moves from energy levels below Fermi energy to energy levels above Fermi energy due to changes in the strength of the bonds, reducing the electron population in the spin-majority channel. This mechanism can be used for local control of the graphene Dirac cone, fine-tuning the in-plane conductance of graphene.