Ferromagnetic-like behavior of Co doped TiO₂ flexible thin films fabricated via co-sputtering for spintronic...

TiO₂:Co thin films on ITO (Indium-tin-oxide)/PET (Poly Ethylene Terephthalate) flexible and glass substrates were fabricated via DC magnetron co-sputtering at room temperature. The samples deposited on glass substrates were subjected to annealing processes at 473 K for 2 h to improve the crystallization of the material. Both TiO₂:Co/ITO/PET and TiO₂:Co/glass thin films exhibited excellent optical properties with more than 80% transmission in the visible region. An increase on ITO/PET surface temperature was detected during the synthesis of the samples; this variation in the ITO substrate ( $$ 2 K) was associated to impact energetic of ion or atoms bombarded during the deposition process. X-ray diffraction measurements evidenced local phases to growth on the flexible substrate; the random distributions of Cobalt crystals into the rutile and anatase phases were associated to a crystalline lattice embedded with magnetic ions. A configuration of small grains and absence of cluster formation on the surface of thin films was observed through SEM and AFM measurements. From this topographic study and MFM measurements evidenced that surface grains were not constituted magnetic domains formation in the thin films. The ferromagnetic-like behavior was observed in a magnetization as function of field measurement by PPMS. M vs H curves at room temperature for TiO₂:Co/ITO/PET thin films, showed the hysteresis loop. The dipolar interaction between Cobalt ions without formation of domains were correlated to the magnetic behavior in the material, as the doping concentration is lower than 12%.