Towards a Room Temperature Organic Spin Valve: Structural, Magnetic and Transport Properties of Fe 3 O 4 /PTCTE/Co Devic
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Towards a Room Temperature Organic Spin Valve: Structural, Magnetic and Transport Properties of Fe3O4/PTCTE/Co Devices Mathieu Palosse1,4, Elena Bedel-Pereira1,4, François Olivié1,4, Isabelle Séguy1,4, Christina Villeneuve1,4, Thomas Blon3,4, Christophe Gatel2,4, Bénédicte Warot-Fonrose2,4, Jean-François Bobo2,4,5 LAAS-CNRS, 7 Av. du Colonel Roche, F-31077 Toulouse, France. CEMES-CNRS, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4, France. LPCNO-INSA, Département de Génie Physique, 135 avenue de Rangueil, 31077 Toulouse Cedex 4, France. 4 Université de Toulouse, UPS, INSA, INP, ISAE; LAAS; CEMES, 118 route de Narbonne, 31062 Toulouse Cedex 9, France. 5 GLAM-MSE, Stanford University, Stanford, CA, United States.
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ABSTRACT This paper describes first steps in preparation of an organic spin valve based on a perylene derivative (PTCTE) sandwiched between magnetite (Fe3O4) and cobalt (Co) ferromagnetic electrodes. MgO(001)/Fe3O4/PTCTE (450 nm)/Co devices were prepared with different Co soft deposition methods: off-axis dc-sputtering or Joule evaporation. Vibrating Sample Magnetometer (VSM) studies of the Fe3O4/PTCTE/Co stacks evidence spin valve behavior with magnetically uncoupled electrodes. These results are correlated with a morphological study by atomic force microscopy (AFM) of each layer and tunneling AFM (TUNA) for the investigation of inhomogeneity of current distribution in the devices. Finally, macroscopic I-V characteristics performed on the same devices will be presented and compared with TUNA results. INTRODUCTION Organic semiconductors (OSCs) have been of high interest in electronic devices for years, because of their tunable characteristics and easy processes of fabrication. OSCs are frequently used in electronic components such as organic light emitting diodes (OLEDs) or organic field effect transistors (OFETs) [1-3]. Organic spintronics is a relatively new and promising research field where organic semiconductors are applied to mediate or control a spin-polarized signal. It is hence a fusion of organic electronics and spintronics. Recently, the field of organic spintronics has particularly attracted attention because of the potentially very long spin relaxation times in organic materials [4]. These large spin relaxation times are due to the small spin-orbit coupling in organic materials, being composed mainly of light carbon and hydrogen atoms. While it took many years to achieve significant spintronics effects in inorganic materials, electrical spin injection and transport in OSCs have produced very encouraging results since the first attempts in 2002 and 2004 [5, 6]. Though Giant Magnetoresistance (GMR) seems to be obtained in most devices, injection and transport of spin-polarized current in organic spintronics are still discussed and the role played by the interfaces between the organic layer and the magnetic electrodes is raising questions. Several aspects of organic spintronics are still lacking, especially efficient spin injection and transport at room temperature. Moreover, most o
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