Epitaxially grown BaM hexaferrite films having uniaxial axis in the film plane for self-biased devices

• Published in: Scientific reports Vol. 7; no. 1; p. 44193
• Main Authors: Zhang, Xiaozhi, Meng, Siqin, Song, Dongsheng, Zhang, Yao, Yue, Zhenxing, Harris, Vincent G.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09.03.2017; Nature Publishing Group
• Subjects: 140/133; 140/146; 639/301/357; 639/925/357/1018; 639/925/357/537; 639/925/357/997; Barium; Electron microscopy; Electrons; Humanities and Social Sciences; Magnetic fields; Magnetic properties; Magnetism; multidisciplinary; Science; Self; Transmission electron microscopy; X-ray diffraction
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep44193

Barium hexaferrite (BaM) films with in-plane c -axis orientation are promising and technically important materials for self-biased magnetic microwave devices. In this work, highly oriented BaM films with different thickness and an in-plane easy axis ( c -axis) of magnetization were grown on a -plane single-crystal sapphire substrates by direct current magnetron sputtering. A procedure involving seed layers, layer-by-layer annealing was adopted to reduce the substrate-induced strains and allow for the growth of thick (~3.44 μm) films. The epitaxial growth of the BaM film on sapphire was revealed by high-resolution transmission electron microscopy with dislocations being observed at the film-substrate interface. The orientation was also verified by X-ray diffraction and more notably, polarized Raman scattering. The magnetic properties and ferromagnetic resonant frequencies were experimentally characterized by a vibrating sample magnetometry and a frequency-swept ferromagnetic resonant flip-chip technique, respectively. The micron-thick BaM films exhibited a large remanence ratio of 0.92 along in-plane easy axis and a small one of 0.09 for the in-plane hard axis loop measurement. The FMR frequency was 50.3 GHz at zero field and reached 57.9 GHz under a magnetic field of 3 kOe, indicating that the epitaxial BaM films with strong self-biased behaviors have good electromagnetic properties in millimeter-wave range.