Giant magnetoresistance enhancement at room-temperature in organic spin valves based on La0.67Sr0.33MnO3 electrodes

We have systematically studied the magnetoresistance (MR) of Alq3-based organic spin valves using as-grown La0.67Sr0.33MnO3 (LSMO), annealed LSMO, and La0.67Ca0.33MnO3 as the bottom electrode. A giant enhancement of MR ratio (more than one order of magnitude) is observed when the optimal annealed LSMO is used, and the measured MR can be as high as 2.2% at room temperature. Below ∼100 K, the temperature dependence of the normalized MR is almost identical with these three electrodes despite the strong difference in Curie temperature (from 250 K to 360 K). We attribute this similar MR temperature dependence to the spin relaxation in Alq3.