Properties of (Fe,Co)-(Ta,W) amorphous alloy films deposited by rf sputtering

Magnetic and thermal properties of the amorphous films of (Fe,Co)100-x(Ta,W)x, ( ) deposited by a rf diode sputtering have been investigated. The amorphous films were obtained for Ta or W content \´X\´ above 14 at.%. The dependence of 4πMs on X of the deposited films was examined in detail. The change of crystal structure of the films from the crystalline phase to the amorphous one at X=14 at.% with increase in X leads to a drastical decrease in 4πMs of the Fe-Ta films. The dependence of 4πMs on X of the Fe-W films is similar to that of the Fe-Ta films. On the other hand, 4πMs of the Co-Ta films decreases gradually with increase in X, even if the crystal structure changes from the crystalline phase to the amorphous one. The maximum 4πMs and the minimum coercive force Hc of the amorphous Co-Ta films are 10 kG and 0.57 Oe, respectively. The crystallization temperatures of the amorphous Co-Ta films are above 800 K, being much higher than those of 3d-transition metal-metalloid amorphous alloys. They may be useful as a soft magnetic material with high thermal Stability.