ORIENTED BARIUM HEXAFERRITE THICK-FILMS GROWN ON C-PLANE AND M-PLANE SAPPHIRE SUBSTRATES

The magnetic and structural properties of thick pulsed laser deposited (PLD) barium hexaferrite (BaM) films grown on c-plane and m-plane sap phire substrates were investigated using X-ray diffraction (XRD), scan ning electron microscopy (SEM), Rutherford backscattering spectroscopy (RBS), vibrating sample magnetometry (VSM), and ferrimagnetic resonan ce (FMR). Previously, BaM thin films (similar to 0.5 mu m) grown on c- plane (0001) sapphire substrates exhibited magnetic properties closely approaching those of single crystal sphere. These films are potential ly useful for thin film millimeter-wave devices such as circulators, i solators, and phase shifters, provided that thick films (e.g., 20 to 1 00 mu m) with suitable magnetic and dielectric properties can be grown . In general, it was found that an increase in film thickness leads to the growth of either textured polycrystalline BaM, which can be loose ly adherent, or delamination of the films. However, well oriented thic k BaM films were grown up to 15 and 20 mu m on the c-plane and m-plane sapphire substrates, respectively, before delamination occurred. The FMR linewidth, Delta H, was 200 Oe at 85 GHz for an annealed 15 mu m t hick PLD BaM film on c-plane sapphire with 4 pi M = 4200 G, H-A = 1600 0 Oe and and XRD omega-scan of 0.51 degrees FWHM about the (008) BaM p lane. The FMR linewidth of PLD BaM films grown on m-plane (1100) sapph ire substrates were greater than 450 Oe with 4 pi M = 4000 G and H-A = 16000 Oe. The m-plane films were magnetically well oriented in the fi lm plane with M(r)/M(s) along with the easy axis greater than 90% for all PLD m-plane BaM films.