Ni-Zn-Co ferrite films prepared at 90°C having μ"=30 at 3 GHz

Ni-Zn-Co ferrite films (Ni_0.16-0.21Zn_0.30-0.36Co_x Fe_2.38-2.46O₄, x=0∼0.16) were deposited by spin-spray ferrite plating method at low temperature of 90°C. All the films had a saturation magnetization M_s larger than 440 emu/cc. A small amount of Co substitution x into Ni-Zn ferrite films changed the magnetic anisotropy in film plane from isotropic to anisotropic and the magnetic easy axis was parallel to the flowing direction of the sprayed solutions on the rotating substrate. The coercivity H_c and anisotropy field H_k took small values of 10 and 25 Oe at x=0.03. The complex permeability was measured in the range 20 MHz-3 GHz and very high static permeability μ\´ of 120 and resonance frequency f_r of 900 MHz were achieved at x=0.03. Exhibiting large μ">30 even at 3 GHz, this Ni-Zn-Co ferrite film is applicable for wave absorbers to suppress the electro-magnetic interference among devices up to microwave frequencies.