Enhanced Spin−Orbit Coupling in Heavy Metals via Molecular Coupling

5d electron comprising metals are used in electronics because of their high spin−orbit coupling (SOC) leading to efficient spin-electric conversion (e.g. the spin Hall, spin torque, and spin Seebeck effects). Development of new routes to dynamic external control of SOC, ideally based on sustainable and benign materials, would be highly desirable for emerging low-power computing technologies such as spin-transfer torque memories and pure spin current circuits.

A collaborative investigation led by the University of Leeds and involving the Scientific Computing Department of STFC-UKRI, the University of Cambridge, Trinity College Dublin and SuperSTEM has discovered that electronic re-hybridisation and charge transfer at Pt/C60 and Ta/C60 hybrid films can enhance the spin Hall magnetoresistance of the composite systems up to a factor of 6 higher than those for the pristine metals, leading to 20−60% increase in the spin Hall angle: a figure of merit for spin-electron conversion. The experimental measurements are qualitatively supported by non-collinear Density Functional Theory simulations run on the ARCHER, UK Materials and Molecular Modelling Hub, and STFC SCARF High Performance Computing facilities.

The simulations suggest a significant SOC enhancement by C60 that penetrates through the Pt layer, concomitant with trends in the magnetic moment of transport electrons acquired via SOC and symmetry breaking. As the charge transfer and re-hybridization between the 5d metal and C60 molecules can be controlled by conventional gating, the findings of the study point to the possibility of dynamically tailoring the SOC and overall spin-electric conversion in metal thin-films interfaced with molecular layers under potentiostatic control.



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