Soft Magnetic Properties of Co-Fe-Al-O Thin Films with High Bs

The structure and properties of Co0.7Fe0.3-Al-O films, prepared by rf magnetron sputtering using oxygen and argon gases, were studied. Soft magnetic properties were found in the films when the compositional ratio of Al-O corresponded to Al2O3. The (Al-O) concentration has a significant influence on the structure and properties of soft magnetic Co0.7Fe0.3-Al-O films. With increasing (Al-O) concentration, the structure of the film changes from micro-crystalline to granular. The coercivity decreases to less than 5 Oe in films containing only a few percent of (Al-O). The magnetostriction also decreases with increasing (Al-O) content, and is almost zero around 27% (Al-O), where the saturation magnetization is near 12 kG. On the other hand, the electrical resistivity and anisotropy field of the films increase with increasing (Al-O) content. By selecting the (Al-O) content in Co0.7Fe0.3-Al-O films, it is possible to find films that have suitable properties for a variety of high-frequency magnetic devices.