Cole-Cole impedance analysis on spin sprayed Ni-Zn-Co ferrite films exhibiting strong magnetic loss in gigahertz range

As the material for realizing gigahertz conducted noise suppressors, Ni-Zn-Co ferrite films (Ni/sub 0.15-0.21/Zn/sub 0.20-0.36/Co/sub x/Fe/sub 2.39-2.58/O/sub 4/, x=0-0.10) were deposited from an aqueous solution by spin spray ferrite plating at 90/spl deg/C. We applied 1.3-kOe bias field parallel to the centrifugal direction of liquid flow on the substrate. The bias field and the Co addition induced an in-plane uniaxial anisotropy with easy axis parallel to the liquid flow (or bias field) direction. The effect was strongest at x=0.03; the complex permeability (/spl mu/=/spl mu/'-j/spl mu/'') along the hard axis exhibited a high-natural ferromagnetic resonance of f/sub r/=1.4 GHz and a strong magnetic loss of /spl mu/''>30 in a wide range between 300 MHz and 3 GHz. Measured along the easy axis, however, /spl mu/' and /spl mu/'' were negligibly small, indicating that the high permeability with strong loss was ascribed to magnetization rotation, with no contribution from domain motion. Cole-Cole impedance (0.1 Hz-1 MHz) plots for each Ni-Zn-Co ferrite film were fitted by a depressed semicircle, whose relaxation angle became largest at x=0.03. This means that the relaxation time in conduction process is most widely dispersed at the same Co content where, as mentioned above, the magnetic loss became strong in a wide frequency range.