Substituted Barium Hexaferrite Films for Planar Integrated Phase Shifters

Abstract

Thick films of scandium-substituted BaScxFe12−xO19 (x=0, 0.4, 0.6) were deposited by pulsed laser ablation deposition onto A-plane (1120) sapphire (Al2O3) substrates to yield highly oriented films having the crystallographic c-axis ([0001]) in the film plane. Selected films were characterized by x-ray diffraction, electron microscopy, magnetometry and torque magnetometry measurements. These structural and magnetic measurements show that dense films have excellent in-plane uniaxial anisotropies and good square loop behaviors. Such films will be useful for planar latched phase shifters that can be integrated into microwave integrated circuits.

Ferrite devices and materials

“…The use of -axis oriented -type hexaferrites for millimeter-wave self-biased circulators has been hindered for similar reasons, but also because of the higher microwave loss [92] that may be fundamental to the electronic structure of the metal ions in the ferrite. Most recently, however, a team at Northeastern University reported the epitaxial deposition of hexaferrite thick films for phase-shifter applications [93].…”

Ferrite Properties and Technology Issues for Improved Microwave Systems

“…For millimeter-wave cases, c-axis hexagonal ferrites can be used in the 3-leg quasi-continuous arrangement sketched in figure 9, with the easy-axis in each part aligned with the corresponding 120-degree configured meanderline patterns. In theory, such a circulator concept could be used over a range extending from microwave to the highest millimeter-wave frequencies by tailoring the chemical compositions of M-type barium ferrite (BaFe 12 O 19 ) by Sc, In, or Al substitutions in place of Fe [13,14].…”