Low-temperature growth of c -axis-oriented Y-type hexagonal ferrite thin films by the polymeric precursor method
- PDF / 230,304 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 15 Downloads / 200 Views
Well-crystallized Ba2Zn2Fe12O22 (Zn2–Y) films with high c-axis oritentation were successfully formed on Ag substrates at low temperature by the polymeric precursor method. A precursor solution with stoichiometric Ba2+, Zn2+, and Fe3+ ions was deposited on the substrates by a dip-coating. The films were then heat-treated at temperatures ranging from 700 to 900 °C. The crystallization process of c-axis-oriented Zn2–Y films occurred at the considerably low temperature of 750 °C, though a small amount of spinel oxides contaminated them. The films had hexagonal grain structures which were developed by increasing the heat-treatment temperature. Magnetization curves of the Zn2–Y film heated at 900 °C clearly indicated that the film had large in-plane magnetic anisotropy and had small in-plane coercivity.
Y-type hexagonal ferrites, Ba2Me2Fe12O22 (Me2–Y), where Me represents divalent ions, are promising candidates for high-frequency microwave device applications.1,2 Thin films of Me2–Y are applicable not only for downsizing the microwave devices but also for fabricating novel hybrid devices with integrated magnetic, electric, and optic circuits. Me2–Y has a ferroxplana structure with much higher initial permeability up to the GHz region compared to the 300-MHz ceiling of the spinel ferrites. This is due to the large in-plane anistropy of Me2–Y constraining magnetization motion inside the c plane. The hexagonal unit cell of Me2–Y has a long c-axis length (43.566 Å for Zn2–Y),3 which is built up from the superposition sequence along the c axis of two fundamental structural blocks. Formation of Me2–Y by traditional ceramic methods based on the solid-state reaction process requires heat treatments at relatively high temperature (1100–1300 °C).4 However, liquid-phase techniques such as the sol-gel process are successfully applied to lower the formation temperature of complex oxide materials.5 The metal ions are atomically mixed in solution, and an inorganic network can be formed by a chemical reaction at low temperature. The large unit cell of Me2–Y makes it difficult to crystallize the structure in the form of thin films. There has been no report obtaining the well-crystallized Me2–Y films, though the thin films of M-type hexagonal ferrites, BaFe12O19, with a magnetoplumbite structure are easily
a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 16, No. 9, Sep 2001
http://journals.cambridge.org
Downloaded: 02 Apr 2015
obtained. The c-axis length of BaFe 12 O 19 is only 23.18 Å, about half of that of Me2–Y. In this communication we successfully report the formation of wellcrystallized Zn 2 –Y films on Ag substrates by the polymeric precursor method. This method is a completely homogeneous process and a cost-effective technique compared to a conventional sol-gel method using metal alkoxides. The procedure consists of preparing coating solutions from the Pechini-type process, depositing precursor films by dip coating, and subsequent heat treatments.6 Single-crystalline ␣–Al2O
Data Loading...
