High remanence ratio of aluminum substituted hexagonal barium ferrite films for self-biased microwave devices

Abstract

A high remanence ratio of hexagonal barium ferrite film is urgently needed for self-biased microwave devices. In this work, the aluminum-substituted hexagonal barium ferrite films (BaFe(12−x)AlxO19) with different substituting concentrations (x = 0, 1.5, 2, 2.5, 3) were deposited on the Al2O3 substrate by pulsed laser deposition method using self-sintered BaFe(12−x)AlxO19 target. Firstly, the targets with different Al concentrations were sintered by the solid phase method and exhibited high dense, uniform microstructure, and high purity. Then, the influence of the Al ions concentration on the crystal structure, morphology, and magnetic and microwave properties of BaFe(12−x)AlxO19 films was studied in detail. Structural characterizations confirm that the Al prefers to substitute for 2a, 4f2 and 2b sites and promotes the grain (formed as single-domain) orientation growth, which results in a decrease in the saturation magnetization, an increase of remanence ratio and anisotropy field. Consequently, a high remanence ratio of 95 % was obtained for BaFe(12−x)AlxO19 film at x = 3, and also displays a high anisotropy field (27.7 kOe), a low saturation magnetization (1758 G) and an appropriate ferromagnetic resonance linewidth (～436 Oe), which can be applied in self-biased devices.