Spin injection and transport characteristics of low-molecular-weight organic semiconductors such as pentacene and bis(l,2,5-thiadiazolo)-p-quinobis(l,3-dithiole) (BTQBT) have been studied utilizing lateral type spin-valve devices with half metal electrodes, LaA0.67Sr0.33MnO3 (LSMO). The LSMO electrodes with a spacing of 200 nm were prepared by electron-beam lithography and dry etching of the epitaxial films grown on MgO substrates. The devices showed clear spin-valve behaviors with a magneto-resistance (MR) ratio up to 29 % at 9.1K. It was found that the MR ratio depended on the crystallinity of organic films as well as on temperature and applied bias voltages

We have prepared layered sandwich structures composed of Co / organic materials / La0.67Sr0.33MnO3 and measured the magnetic field effect on electrical resistance. We inserted various OMs including pentacene, C60, 8-hydroxy-quinoline aluminum and titanyl-phthalocyanine with a thickness in the range from 200 nm to 1,000 nm. All devises prepared showed clear spin-valve characteristics with magneto-resistance (MR) ratios of approximately a few to 10% at low temperature. It was found that spins were transported in rather thick organic films, and the polarity of MR depended upon materials inserted and their film thickness.