Organic Spin Valves with Characteristics of Inelastic Tunneling and Hopping Transport

We report on the inelastic scattering characteristics of an organic-based spin valve with a thin organic barrier of 3,4,9,10-perylene-teracarboxylic dianhydride (PTCDA) dusted with alumina at organic/ferromagnetic interfaces. Spin injection with magnetoresistance up to 12\% at room temperature was achieved. In the inelastic tunneling spectrum, the observation of characteristic vibrational loss peak of organic spacer provides direct evidence of the interplay between the spin-polarized electrons and the organic molecules. The spin-dependent transport mechanism can be further described with a model of combined tunneling and hopping processes as verified by experiments as a function of organic layer thickness.