Effect of Zr and Nb additions on the high-frequency magnetic properties of Co_85-(x+y)Zr_3+xNb_12+y films

This high-frequency magnetic properties of 250-nm-thick Co_85-(x+y)Zr_3+xNb_12+y (x: 0-5.5, y: 0-11.0) amorphous films are examined as functions of Zr (x) and Nb (y) concentrations. Both x and y influence the high-frequency magnetic properties. In the case of x<3.0 and y≤5.0, each permeability spectrum appears, but increasing x and y decreases the ferromagnetic resonance (FMR) frequency from 1.20 GHz to 0.41GHz and increases the effective damping constant from 0.15 to 0.43. For x=3.0 and y=8.2, although the permeability spectrum disappears, the effective damping constant is estimated to be approximately 0.82. In contrast, the high-frequency magnetic properties cannot be obtained for x=5.5 and y=11.0. Hence, appropriately selecting both Zr and Nb concentrations should effectively control the high-frequency magnetic properties. This finding should be of interest from the viewpoint of new thin film applications, such as microscopic electromagnetic compatibility (EMC), in which properly adjusting the permeability and FMR profiles is vital.