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

Abstract

We investigated curvature-enhanced spin-orbit coupling (SOC) and spinterface effect in carbon-based organic spin valves (OSVs) using buckyball C60 and C70 molecules. Since the naturally abundant 12C has spinless nuclear, the materials have negligible hyperfine interaction (HFI) and the same intrinsic SOC, but different curvature SOC due to their distinct curvatures. We fitted the thickness dependence of magnetoresistance (MR) in OSVs at various temperatures using the modified Jullière equation. We found that the spin diffusion length in the C70 film is above 120 nm, clearly longer than that in C60 film at all temperatures. The effective SOC ratio of the C70 film to the C60 film was estimated to be about 0.8. This was confirmed by the magneto-electroluminescence (MEL) measurement in fullerene-based light emitting diodes (LED). Next, the effective spin polarization in C70-based OSVs is smaller than that in C60-based OSVs implying that they have different spinterface effect. First principle calculation study shows that the spin polarization of the dz2 orbital electrons of Co atoms contacted with C60 is larger causing better effective spin polarization at the interface.

Enhanced room-temperature spin Seebeck effect in a YIG/C60/Pt layered heterostructure

“…As the spin diffusion length of C 60 (λ C 60 ∼100 nm) 13 is greater than that of Pt (∼2 nm), more spin current is expected to reach the Pt layer. According to Eq.…”

“…The deposition of this semiconductor between the insulator (YIG) and the metal (Pt) is expected to rectify the spin conductivity mismatch problem. Since C 60 possesses a long spin diffusion length (∼100 nm), 13 which is substantially longer than that of Pt (∼2 nm), the presence of C 60 can improve the spin mixing conductance of the YIG/Pt interface. Effects of the added C 60 layer on the PMA of the YIG film are probed by radio-frequency (RF) transverse susceptibility measurements.…”

A key role of tensile strain and surface termination in formation and properties of La0.7Sr0.3MnO3 composites with carbon nanotubes

“…The analysis of composites' electronic structure ( Figure 4) shows that it remains almost the same as for the bare LSMO in both cases. Although composites are almost totally spin polarized, it can be seen that this is due to LSMO slab while nanotubes' spin-up and spin-down partial densities of states are of an equal intensity (spin polarization values are ~1.7% and ~0.3% for CNT (5,5) and CNT(9,0), respectively, the absence of visible spin polarization is also confirmed by the spatial spin density distribution).…”

“…Half-metallic La 0.7 Sr 0.3 MnO 3 (LSMO) is widely used in spintronic and spincaloritronic devices due to its unique properties like half-metallic nature and high Curie temperature (Т с =370К, the highest among substituted lanthanum manganites) [1][2][3][4][5]. Nanosized materials are of particular interest since their usage allows one to significantly increase the efficiency of the devices.…”

A review on organic spintronic materials and devices: I. Magnetic field effect on organic light emitting diodes

“…Since the SOC in this case is quite large compared to HFI strength, the OMAR response is normally quenched and its HWHM is significantly broader [53,55,101]. In addition to intrinsic SOC, recent study shows that the curvatureenhanced SOC might also play an important role on electron spin dynamics in organic substances [102]. In the following section, we only focus our discussion on OMAR mechanisms in conventional OSCs only where HFI dominates.…”