High-frequency magnetic properties of W-type barium-ferrite BaZn2-xCoxFe16O27 composites

The static and high frequency magnetic properties have been studied for BaW ferrites BaZn2-xCoxFe16O27 with x=0, 0.5, 0.7, 1.0, 1.5, and 2.0. The results showed that Co ions are able to modify the anisotropy from c axis to c plane at x=0.6-0.7. For the BaW composites with c-plane anisotropy, as the Co concentration x increases, the resonance frequencies f(R) are shifted to higher frequency, from 2.5 GHz at x=0.7 to 12.0 GHz at x=1.5. The permeabilities mu(0)(') and mu(max)(') are 2.4-2.2 and similar to0.8, respectively, for composites with 35% (by volume) BaW ferrite powders at x=0.7 and 1.0. The parameters indicate that BaZn2-xCoxFe16O27 composites have suitable high frequency properties for use as electromagnetic materials with low reflectivity at microwave frequencies. In addition, for BaW composites with c-axis anisotropy, there exist both the domain wall and natural resonances. However, only natural resonance is observed for composites with c-plane anisotropy. (C) 2003 American Institute of Physics.