Development of FeCo-based thin films for gigahertz applications

For improving high-frequency characteristics and soft magnetic properties of (Fe7Co3)B-based thin films, the effects of Ni addition and an oblique deposition method on the microstructures have been examined. The Ni addition to (Fe7Co3)B films was found to enhance B segregation on grain boundaries, which resulted in the formation of a well-defined columnar structure and the increase of film resistivity. Utilizing the columnar structure, large in-plane anisotropy was induced by an oblique deposition method which enabled the control of the inclination angle of the columns. As a result, the ferromagnetic resonance of (Fe7Co3)(71)Ni7B22 thin films reached 6.2 GHz.