Microwave Resonance Linewidths in Substituted Single-Crystal Barium Ferrite

Abstract

Ferromagnetic resonance linewidth measurements were performed at 37.6 GHz on substituted barium ferrite, BaZnx Tix Fe12−2xO19, where x varies from 1.0 to 2.5 in the melt. Crystals were synthesized by two growth procedures; a modified pulling technique and a free nucleation method from slow cooling BaO/B2O3 fluxes. The uniaxial anisotropy field Ha varied from 5400 to 11 100 Oe; Tc from 351° to 613°K, making the material of considerable interest for microwave device applications. Cavity perturbation techniques were used with polished spherical samples 15–20 mil in diameter. Variation in values of x have a large effect on the linewidths obtained. The linewidth decreases with increasing x to a minimum at 1.5 and then increases as x exceeds 1.5. At x = 1.5, resonance linewidths of 36 Oe on pulled crystals and 42 Oe on free nucleated crystals were observed.