Pulsed laser-deposited single-crystal LiZn-ferrite films with low microwave loss

Abstract

Lithium zinc ferrite (LiZnF) films were prepared for a wide range of deposition parameters. Bulk LiZnF rather than pure Li ferrite targets were used to mediate the mismatch problem between the film and the MgO substrate. Preparation conditions were optimized to give single phase epitaxial films with half power ferromagnetic-resonance (FMR) linewidths of as low as 57 Oe at 9.5 GHz. The films were deposited on (100)-plane MgO substrates with a KrF excimer laser at a wavelength of 248 nm. The minimum linewidth films with a thickness of 0.70 μm were obtained for an oxygen partial pressure of 400 mTorr, a substrate temperature of 800 °C, and a laser fluence of 1.7J∕cm2. X-ray diffraction pattern indicated a pure LiZn phase with local normal axis deviations below 0.05°. The FMR profiles were measured at 9.5 GHz with the static field perpendicular and parallel to the film plane, and as a function of rotation angle for in-plane fields. The data yielded a saturation induction 4πMs value of 2.730 kG, about the same as for a bulk, and cubic anisotropy, with a first-order cubic anisotropy energy constant K1 of about 7.33×103ergs∕cm3, a factor of five or smaller than that for a bulk LiZn ferrite.