Abstract. Organic spintronics has been an active research field since the demonstration of large magnetoresistance in a thick organic spin valve, in which carrier spins are injected into the organic… Click to show full abstract
Abstract. Organic spintronics has been an active research field since the demonstration of large magnetoresistance in a thick organic spin valve, in which carrier spins are injected into the organic film sandwiched between two ferromagnetic electrodes. In such spin-injection devices, spin relaxation time and spin diffusion length are key properties that control spin-dependent transport and dictate the device design. Here, we compare spin relaxation and diffusion behaviors in organic solids due to spin-dependent interactions including spin-orbit coupling (SOC), hyperfine interaction (HFI), and exchange. It is found that for SOC-induced spin relaxation, the spin diffusion length is essentially determined by the spin admixture parameter and insensitive to magnetic field and carrier hopping rate, whereas for HFI-induced spin relaxation, it increases rapidly with both the magnetic field and hopping rate. In devices with high-density carriers, where exchange-induced spin motion dominates over carrier hopping, the spin diffusion length is limited by SOC.
               
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