Manganite/Alq3 interfaces investigated by impedance spectroscopy technique

With the general objective of studying interfaces between ferromagnetic materials and organic semiconductors, we report ac impedance investigations on La0.7Sr0.3MnO3 (LSMO)/tris(8-hydroxyquinoline)aluminium (Alq3)/Al and Indium Tin Oxide (ITO)/Alq3/Al heterostructures, in the frequency range between 20 Hz and 1 MHz. The comparison of the equivalent circuits deduced to fit the experimental ac responses allows isolating a specific RC contribution which can be attributed to the LSMO/Alq3 interface region. Using the information obtained from our ac measurements, we propose a model which fits the temperature dependence of the magnetoresistance in spin valves combining LSMO electrodes and Alq3 layers. (C) 2008 Elsevier B.V. All rights reserved.