Synthesis of textured barium hexaferrite films on silicon substrates with amorphous Al$_2$O$_3$|Si$_3$N$_4$ coating

BaFe$_{12}$O$_{19}$ thin films were synthesized by ion-beam sputtering on amorphous Al$_2$O$_3$|Si$_3$N$_4$ structures. Immediately after sputtering, the BaFe$_{12}$O$_{19}$ films are amorphous, but can be converted to a crystalline state by annealing. In this case, under certain conditions, a (00l) texture spontaneously forms in such films, which allows them to be used for designing and creating planar microwave devices, spintronics and magnetic memory devices. However, due to heat treatment, mechanical stresses arise in the BaFe$_{12}$O$_{19}$| Al$_2$O$_3$|Si$_3$N$_4$ structure, leading to the formation of macroscopic defects. In this work, we study the possibility of reducing stresses by additional annealing of the Al$_2$O$_3$3 and Si$_3$N$_4$ layers at 900$^\circ$C and varying the Al$_2$O$_3$ thickness in order to obtain defect-free BaFe$_{12}$O$_{19}$ (00l) films.