Preparation of ferrite thin films

Many specialised applications of magnetic materials involve the utilisation of ferrite thin films, such as magnetic and magnetooptic recording media, microwave devices in integrated circuits and coatings for microwave shielding. To prepare these ferrite thin fihns, a wide variety of techniques has been devised. 

---

Fig. 3.26. Schematic sol-gel process for the preparation of ferrite thin films. (Adapted from Tanaka et al, 1989.)...

Fig. 3.29. Preparation of ferrite thin films using arc plasma. (Adapted from Harris et aL, 1970.)...

Chemical vapour deposition (CVD), or more specifically, organo-metallic CVD can also be used to prepare ferrite thin films (Itoh, Takeda Naka, 1986). A mixture of acetylacetonate complexes of the desired metal is evaporated in a quartz boat (number 1 in Fig. 3.27) and is reacted with O2, which is introduced directly in the deposition zone. By adding a second furnace (B), an additional component evaporating at a different temperature can be transported to the substrate. Glass or MgO single crystals can be used as the substrates an annealing up to 1(X)0°C is performed on the film to improve its crystallisation. Spinel thin films (Ni, Ni-Zn) have been prepared by this method. 

Suzuki, K., Namikawa, T. Yamazaki, Y. (1988). Preparation of zinc- and aluminium-substituted cobalt-ferrite thin films and their Faraday rotation. Japanese Journal of Applied Physics, 27, 361-5. 

Arurault L, Monsang P, Salley J, Bes RS. Electrochemical preparation of adherent ceria coatings on ferritic stainless steel. Thin Solid Films. 2004 466 75-80. DOI 10.1016/ j.tsf.2004.02.039. 

Although most materials grown by LPE have the garnet structure, spinel ferrites can be grown similarly, and films of hexagonal ferrites are also prepared ". Only small quantities are required, and the crystallographic quality of the film can be high, but a suitable substrate is required and the measurement or device must be made on a thin layer rather than a bulk crystal. 

Ferrites can be prepared by almost all the existing techniques of solid state chemistry, leading to a very wide variety of forms polycrystalline aggregates, thin and thick films, single crystals. Some of these methods have been developed to prepare ferrites with specific microstructures. The oldest one, the ceramic method, involves the same operations as the classical techniques for fabrication of conventional ceramics. This explains the origin of the term magnetic ceramics. Many of the techniques recently developed consist of improvements in one or several of the basic operations of ceramic fabrication. 

---