Preparation and Magnetic Properties of SrFe₁₂O₁₉Ferrites Suitable for Use in Self-Biased LTCC Circulators

Abstract

Strontium ferrites with different Bi 2 O 3 content are prepared by the solid phase method, and their magnetic properties are investigated primarily. The Bi 2 O 3 additive and sintering temperature separately exhibit a strong effect on the sintering density, crystal structure, and magnetic properties of the ferrites. As to the ferrites with 3 wt% Bi 2 O 3 , the relatively high sintering density ρ s , saturation magnetization M s , and intrinsic coercivity H ci can be obtained at a low sintering temperature of 900°C even much lower. Furthermore, the effective magnetic anisotropy constant K eff and magnetic anisotropy field H a of the ferrites are calculated from the magnetization curve by the law of approach to saturation. It is suggested that the low-temperature sintered SrFe 12 O 19 ferrites with M s of 285.6 kA/m and H a of 1564.6 kA/m possess a significant potentiality for applying in the self-biased low-temperature co-fired ceramics circulators from 34 to 40 GHz.