Paper MI-WeM3
Progress toward Understanding the Sign of Spin-Polarization at Interfaces in Organic Spin-Valves

Wednesday, November 2, 2011, 8:40 am, Room 105

In this talk I will present results from a systematic study to understand the role of LiF, Al₂O₃, and MgO tunnel barriers in organic spin-valves. The overall aim of this work is to better quantify the degree of spin-polarized electron injection and extraction at ferromagnetic metal/organic semiconductor interfaces. In general we find that spin-valves made with two ferromagnetic transition metals has a positive magnetoresistance. However, when one of the ferromagnetic metals is exchanged with La_0.67Sr_0.33MnO₃, the sign of the magnetoresistance is inverted. In addition the spin-polarized tunneling measurements the structural, electronic, and magnetic properties of these interfaces have been thoroughly investigated by cross-sectional transmission microscopy, photoelectron spectroscopy, and polarized neutron reflectometry. These results will be compared to other findings in the literature in order to summarize the current status of spin-polarized electron transport across organic semiconductor/insulator/ferromagnetic metal interfaces.