Structural, electronic and magnetic characterization of SrTiO₃/La_0.67Sr_0.34MnO₃/Fe-Phthalocyanine/Co

Understanding how to incorporate organic materials in spintronic devices is still a frontier research in spite of intensive investigation. Several organic spin-valves have been designed as two magnetic electrodes sandwiching an organic film that displayed magneto-resistive behavior. Here, we investigated Co(0.5nm)/FePc(~1nm)/La_0.7Sr_0.3MnO₃(~60nm)/SrTiO3 multilayered sample. LSMO and Co are the most used electrodes for organic spintronics, in particular LSMO has a stable surface to oxidization and excellent magnetic polarization at room temperature. FePc is a quasiplanar heterocyclic macrocycle molecule with high conjugation, already showing FM order when in contact with Co FM film. The heterostructure was prepared using the surface facility tools (Pulser Laser, Organic and Inorganic Molecular Beam Deposition Chambers) and characterized (X-ray Photoemission and Absorption) IN-SITU at PGM beamline, LNLS. The chemical interaction between FePc and Co has been observed as modification of X-ray core level (C 1s and N 1s) and absorption (at Fe and Co L2,3) spectral line shapes. The magnetic response of each component of the heterostructure was monitored by X-ray Magnetic Circular Dichroism, whereas the overall magnetic properties are probed with a vibrating sample magnetometer. Each component show ferromagnetic coupling, however the overall magnetization presents the signature of spin reorientation at temperature between 2 and 100K. These results help in understanding the control of magnetic properties of hybrid organic/inorganic heterostructure. (author)