Static magnetic and microwave properties of Li-ferrite films prepared by pulsed laser deposition

Abstract

Highly textured Li-ferrite films have been synthesized by pulsed laser deposition from bulk targets onto c-plane sapphire substrates. For substrate temperatures approaching 1000 °C the growth mode was predominantly (333). A similar growth mode was recently reported for Ni-ferrite films grown onto c-plane sapphire substrates. The films were 4–8 μm thick and were grown at deposition rates of 3–5 Å/s at oxygen partial pressures of 200–400 mTorr. Magnetic measurements were made by SQUID and 9.5 GHz ferromagnetic resonance (FMR) on the as deposited films. Textured Li-ferrite films with x-ray diffractometer intensity ratios of I(333)/I(311)=10.3 for films made in 200 mTorr oxygen and 14.5 for films made in 400 mTorr oxygen exhibited room temperature in-plane intrinsic coercivities of <100 Oe for SQUID magnetometer measurements. Highly (333) textured Li-ferrite films made in 400 mTorr oxygen exhibited clean symmetric FMR absorption lines with a derivative peak-to-peak linewidth of 335 Oe for the in-plane static field configuration. The FMR profiles for the perpendicular-to-plane field configuration were highly distorted. The magnetization versus field measurements and the in-plane FMR field position yielded saturation flux density 4πMs and effective saturation flux density 4πMeff values of 3.6–4.0 kG and 3.56–3.70 kG, respectively. These values are in the same range as for bulk Li-ferrite. The in-plane FMR linewidths were significantly larger than expected for bulk single crystals or large grain size, dense polycrystals.