Curvature-enhanced Spin-orbit Coupling and Spinterface Effect in Fullerene-based Spin Valves

Area of Science:

• Spintronics
• Organic electronics
• Materials science

Background:

• Organic spin valves (OSVs) offer potential for spintronic applications.
• Carbon allotropes like C60 and C70 present unique electronic and structural properties.
• Spin-orbit coupling (SOC) and spinterface effects are crucial for OSV performance.

Purpose of the Study:

• To investigate the influence of molecular curvature on spin-orbit coupling (SOC) and spinterface effects in C60 and C70 based OSVs.
• To compare the spin diffusion length and effective spin polarization in C60 and C70 films.
• To elucidate the role of the interface between ferromagnetic electrodes and fullerene layers.

Main Methods:

• Fabrication and characterization of OSVs using C60 and C70 films.
• Magnetoresistance (MR) measurements at various temperatures.
• Magneto-electroluminescence (MEL) measurements in fullerene-based light-emitting diodes (LEDs).
• First-principles calculations of electronic structure and spin polarization.

Main Results:

• The spin diffusion length in C70 films exceeds 120 nm, significantly longer than in C60 films across all measured temperatures.
• An effective SOC ratio of approximately 0.8 was estimated for C70 relative to C60.
• C60-based OSVs showed higher effective spin polarization than C70-based OSVs, attributed to the interface with cobalt electrodes.
• First-principles calculations confirmed higher spin polarization for Co atoms interacting with C60.

Conclusions:

• Molecular curvature significantly impacts curvature-enhanced SOC in fullerene-based OSVs.
• C70 exhibits superior spin transport properties compared to C60 due to its longer spin diffusion length.
• The spinterface effect plays a critical role in determining the effective spin polarization at the electrode-organic interface.