Preparation of yttrium iron garnet thin films by mist chemical vapor deposition method and their magneto-optical properties

Abstract

Polycrystalline and epitaxial thin films composed of a single phase of yttrium iron garnet (YIG) have been synthesized on silica glass and singlecrystalline gadolinium gallium garnet substrates, respectively, by the mist chemical vapor deposition (CVD) method. The element Y can be found in the deposited thin films only when an aprotic polar solvent such as acetone is employed for the preparation of the precursor solutions. The crystal structure, magnetic properties, and magneto-optical properties of the thin films are explored. The maximum Faraday rotation angle observed in the present epitaxial YIG thin film is 3.66°/µm at 441 nm, as far as we know, which is higher than those reported for YIG films prepared by other methods, suggesting that the mist CVD method is effective for obtaining epitaxial thin films of multiple oxides.

Faraday effect of bismuth iron garnet thin film prepared by mist CVD method

“…15,16) In the previous study, we successfully synthesized YIG thin film, a prototype of garnet-type ferrite as described above, by using the mist CVD method. 17) We could obtain dense and homogeneous thin films with excellent magnetic and magneto-optical properties, suggesting that the mist CVD method is also effective for obtaining high quality thin films of multiple oxides. Besides, the mist CVD process has advantages of high deposition rate and small fluctuation in composition.…”

“…35,36) For the present thin film, the magnetization reaches about 1620 G. Similarly to MOD method, the mist CVD method is thought to suppress the formation of oxygen vacancies because the reaction proceeds in air, and consequently, all the Fe ions present as the trivalent state, as demonstrated by the XPS data, leading to the high value of M S . 17) Not only the magnetization but optical absorption is an important factor to evaluate the practical performance of magneto-optical materials such as BIG. The optical transmittance spectrum of the epitaxial BIG thin film 230 nm thick is given as open circles in Fig.…”

Incorporation of yttrium to yttrium iron garnet thin films fabricated by mist CVD

“…Thus, methanol was chosen as the most appropriate solvent. Note that this choice was different from that in the earlier work of Yao et al 23) The temperature dependence of the film thickness is plotted in Fig. 1.…”

“…[17][18][19][20][21][22] Yao et al previously grew YIG thin films by mist CVD. 23) They found that the [Y]=[Fe] ratio in the solution was 1.5, while that in thin films was 0.6. However, this large difference in the [Y]=[Fe] ratio between the solution and the thin films was not discussed in detail, and only the activation energy difference of yttrium and iron was provided.…”

“…However, this large difference in the [Y]=[Fe] ratio between the solution and the thin films was not discussed in detail, and only the activation energy difference of yttrium and iron was provided. 23) Generally, Y 3 Fe 5 O 12 is more stable than other alloys of yttrium and iron-related oxides, but the reasons for the large excess amount of yttrium necessary to prepare YIG thin films were not well understood. In this work, we focused on the development of a thermodynamic model to explain the experimental results, using thermogravimetric differential thermal analyses (TG-DTA) of yttrium acetylacetonate [Y(acac) 3 1 nH 2 O] and iron acetylacetonate [Fe(acac) 3 ] metal salt precursors.…”