The origin of interfacial electronic and magnetic degradation for a ferromagnet atop organic conjugated molecules

Over the past years, spin and magnetic-field effects in devices operate by means of an organic spin valve using organic conjugated materials. As the interfacial properties in a ferromagnet-organic hybrid structure critically affect the performance of organic spintronic devices, understanding the interplay between interfaces in these hybrid structures becomes important. To study the interfacial electronic and magnetic properties of Co/Pentacene(Pc)/Co/Cr/Si(1 0 0) in a vertical pseudo-spin-valve structure, we employed synchrotron photoelectron spectra (PES), near-edge X-ray absorption fine structure (NEXAFS) and the magneto-optical Kerr effect (MOKE) to examine the interfacial hybrid state for Pc on Co (Co/Pc) and vice versa for Pc/Co bilayers. The evidences from PES, NEXAFS and MOKE suggest an asymmetric electronic and magnetic interface for Co/Pc and Pc/Co. The Co/Pc interface presents a chemically stable surface, but Pc/Co displays a reacted interface with a magnetically dead layer on the surface. Assisted with a calculation based on the density-functional theory, we elucidate the possible origin of the electronic and magnetic degradation for Co atop Pc in the interfacial regime. (C) 2010 Elsevier B.V. All rights reserved.