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Nanoindentation and magneto-optical study of oxidized Co thin films S. R. Mishra1, J. Rho2, G. Sherfy1, M. Roy2, and T. Buckner1 1. Department of Physics, The University of Memphis, Memphis, TN 38152 2. Department of Biomedical Engineering, The University of Memphis, TN, 38152 ABSTRACT We have studied the mechanical and magneto-optical properties of postdeposition oxidized Co thin films. Oxidization process leads to the formation of double-layered structure of cobalt oxide on top of metallic cobalt. The nanoindentation measurements show decrease in hardness and Young’s modulus at low annealing temperature and are related to increasing porosity of the film. The magneto-optical Kerr effect (MOKE) reveals dependence of the MOKE spectra on annealing temperature. The increased coercivity of the annealed films has been observed by MOKE and is related to the structure of the film. INTRODUCTION Multilayer structures consisting of alternating nonmagnetic and magneto-optically active layers are of significant importance in the field of magneto-optical recording. The magnetooptical detector measures the Kerr rotation (Magneto optical Kerr effect) for detecting the bit information. The enhancement in the Kerr rotation signal has been demonstrated in various bilayers and rare-earth intermetallic layers [1,2,3]. It has been also suggested that considerable enhancement in the magneto-optical property can be obtained in polycrystalline Co films by postdeposition annealing in air or oxygen [4]. The “natural”oxide layers form on top of metallic Co leads to magneto-optically active bilayers. Thus, such a postdeposition processing could become technologically relevant. Over and above the cobalt oxide is generally used in two covalent states CoO and Co3O4 in ceramic coating industry. The later form is the most commonly used in manufacturing ceramics, glass and enamels coating, and in preparing catalyst and cobalt metal powder. If the advantages of such hard films are to be fully employed in improving the surface properties of engineering component, it is necessary to understand the mechanism by which surface properties are changed and enhanced. This mechanism can be characterized by understanding the interrelation between surface roughness, surface hardness, and contact stress. To assess the mechanical properties of the coated system nanoindentation is used preferentially particularly because of very low loads and displacements are available and has ability to measure indentation contacts as shallow as 20 nm [5,6,7,8]. In the report, the mechanical and magneto-optical behavior of nanocrystalline cobalt oxide thin films prepared by e-beam evaporation is presented. The hardness and elastic modulus of a series of films annealed at different temperature has been measured as a function of contact depth and has been correlated with the microstructure. The magneto-optical measurements were performed to understand the magnetic properties of the surface in the presence of oxide layer. EXPERIMENTAL The Co films were prepared by e-beam evaporation