Large room-temperature magnetoresistance and temperature-dependent magnetoresistance inversion in La 0.67Sr 0.33MnO 3/Alq 3 - Co nanocomposites/Co devices

Abstract

Large room-temperature (RT) magnetoresistance (MR) and temperature-dependent MR inversion have been observed in tris (8-hydroxyquinoline) aluminum (Alq 3)-cobalt nanocomposites-based organic–inorganic hybrid devices. Negative MR–high resistance for parallel electrodes configuration — due to magnetization reversal of ferromagnetic (FM) electrodes has been observed at low temperatures. As the temperature increases, the MR undergoes a sign change. At room temperature, a positive MR of ∼9.7% with the resistivity dropping monotonously with increasing magnetic fields has been observed. The RT MR is about two orders of magnitude of that in organic-FM nanocomposites measured with nonmagnetic electrodes. The enhancement of RT MR is attributed to the injection of spin polarized carriers into Alq 3-Co nanocomposites.