Bi-substituted yttrium iron garnet, Y3-xBixFe5O12 (Bi:YIG, x = 1, 1.5), films were prepared on Gd3Ga5O12 (111) substrates by metal-organic decomposition (MOD) method to use as MO indicator films. Those films had the in-plane magnetic anisotropy and Faraday rotation as large as that of the single crystal and do not show prominent magnetic domain structure, which is often observed in single crystalline garnet films grown by liquid phase epitaxy method. Disappearance o magnetic domain structure can be attributed to a granular structure with a grain size of 50 nm in Bi:YIG thin films. The characteristics are suitable for MO indicator films to visualize a stray magnetic field strayed from a specimen. In this paper, MO imaging of Nb films with groove patterns is demonstrated.Key wor ds : magneto-optical imaging, magneto optical indicator film, Bi-substituted garnet, superconductor
I ntro ductionMagnetic imaging technique utilizing magneto-optical (MO) effect has been attracting attentions because it has comprehensive advantages of a fast measurement, a high resolution, a wide range of operating temperature, a quantitative evaluation of magnetic fluxes, etc., compared with recently developed magnetic microscopes such as a magnetic force microscope, a SQUID microscope etc. 1) . Bi substituted rare-earth iron garnet films have been used as an MO indicator film that makes magnetic flux distribution visible by utilizing its huge Faraday rotation in the visible to infrared range.In addition to a high sensitivity of approximately 1 Oe, to obtain a high resolution that is high enough to be within the optical limit in MO imaging, high quality garnet thin films with a thickness as thin as 1 μm are required, since the magnetic flux generated by the samples rapidly diminishes with distance from the samples 2) . Moreover, the zigzag-shaped magnetic domain structure often observed in single crystalline garnet films is a problem which should be solved, because it disturbs the MO observation, as discussed later.Bi substituted garnet films have been prepared by several techniques, such as a liquid phase epitaxy (LPE) 3) , an RF magnetron sputtering 4) and a thermal decomposition method [5][6][7][8] , etc.In those technique, MOD methods are advantageous not only for the homogeneity of the thin film, the controllability of composition, and the formation over a large area, but also for the good productivity, since MOD solutions have good stability for more than several years 9) . In this paper, we report on Bi-substitute yttrium iron garnet thin films for MO indicator films without zigzag-shaped magnetic domains by a metal organic decomposition (MOD) method. The total concentration of carboxylates in those MOD solutions was fixed at 3%. It should be noted that these MOD solutions are stable and precipitation or other changes have not been observed over two years.These solutions were spin-coated on the gadolinium gallium garnet, Gd3Ga5O12, (111) substrates in a 2 step process: 500 rpm for 5 s and 3000 rpm for 30 s, followed by drying at 1...