Titanium dioxide - Cobalt magnetic film and method of its manufacture

Abstract

A titanium dioxide.cobalt magnetic film is provided that is useful to make up a photocatalyst having high catalytic capability, a semiconductor material having an optical, an electrical and a magnetic function all in combination, and a transparent magnet. The titanium dioxide.cobalt magnetic film has a composition expressed by chemical formula: Ti 1-x Co x O 2 where 0<x≦0.3, wherein a Ti atom at its lattice position is replaced with a Co atom, and the magnetic film is a film epitaxially grown on a single crystal substrate. The magnetic film has either anatase or rutile crystalline structure, has its band gap energy varying in a range between 3.13 eV and 3.33 eV according to the concentration of Co atoms replaced for Ti atoms at their lattice positions, is capable of retaining its magnetization even at a temperature higher than a room temperature, and is also transparent to a visible light. I the manufacture of the titanium dioxide.cobalt magnetic film, a target having TiO 2 and Co mixed together at a selected mixing ratio is prepared, placed in a vacuum chamber provided with an atmosphere with a selected oxygen pressure therein, and irradiated in the vacuum chamber with a selected laser light under selected irradiating conditions to cause TiO 2 and Co to evaporate from the target and a layer of TiO 2 .Co to grow in a single crystal substrate that is heated in the vacuum chamber.

1 - 8 . (canceled)  
     
     
         9 . A method of making a titanium dioxide.cobalt magnetic film, characterized in that it comprises the steps of: 
 preparing a target having TiO 2  and Co mixed together at a selected mixing ratio, and placing a single crystal substrate and said target in a vacuum chamber provided with an atmosphere with a selected oxygen pressure therein; and    in said vacuum chamber, heating said substrate to a selected substrate temperature and irradiating said target with a selected laser light under selected irradiating conditions to cause said TiO 2  and Co to evaporate from said target and a film of TiO 2 .Co epitaxially grow on said heated single crystal substrates    wherein said film of TiO 2 .Co is expressed by chemical formula: Ti 1-x Co x O 2  where 0<x≦0.3, and wherein a Ti atom at its lattice position is replaced with a Co atom.    
     
     
         10 . A method of making a titanium dioxide.cobalt magnetic film, as set forth in  claim 9 , characterized in that said selected oxygen pressure ranges between 10 −5  and 10 −6  Torr, said selected substrate temperature ranges between 500 and 700° C. said selected laser light is a KrF-excimer laser light applied in the form of a succession of laser pulses, and said selected irradiating conditions include a per pulse power density of said laser light ranging from 1 to 2 joules/cm 2  and a rate of irradiation with the laser pulses ranging between 1 and 10 Hz.  
     
     
         11 . A method of making a titanium dioxide.cobalt magnetic film, as set forth in  claim 10 , characterized in that it further comprises preparing a second target composed exclusively of TiO 2  and placing said second target in said vacuum chamber, and irradiating the first mentioned target and said second target alternately with laser pulses of said selected laser light at a selected ratio in number corresponding to a selected concentration of Co in TiO 2 .Co composing said film, thereby permitting a film of TiO 2 .Co with said selected Co concentration to grow on said heated single crystal substrate.  
     
     
         12 - 15 . (canceled)