1999 年 23 巻 1_2 号 p. 76-78
The relationship between the tunnel-type magnetoresistance(TMR) and the structure of metal-nonmetal granular system (Fe-Co)-Al-O films has been examined. Films were prepared by a tandem deposition method with rotating a substrate holder. The average diameter of metallic granules is found to decrease with an increase in the rotating speed of substrate holder without any change of film composition. And the MR ratio increases with a decrease of the diameter of metallic granules. The influence of the granule diameter on the MR ratio is discussed by so-called coulomb blockade effect. Furthermore, we studied the effect of a substrate temperature(Tsub.) on the MR and the structure of films. The MR ratio and electrical resistivity of the films increase with an increase of Tsub.. The magnetization measurements suggests that these increases are related with the decrease of the amount of magnetic impurities in the Al-oxide intergranule. The phase separation between the metallic granule and the oxide intergranule may take place in the film prepared on the higher Tsub..
