Magneto-optical Indicator Garnet Films Grown by Metal-organic Decomposition Method

Abstract

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...

Nd3-xBixFe4GaO12(x = 2, 2.5) films on glass substrates prepared by MOD method

“…We have reported that metal-organic decomposition ( MOD) method is promising to obtain high quality garnet films with high-bismuth content because they are advantageous not only for homogeneity of the thin film, the controllability of composition, and formation over large area but also for the good productivity and stability of the MOD solution for more than several years [11][12][13][14][15][16] . In previous work, we have also reported that Nd 2 BiFe 4 GaO 12 (Bi1:NIGG) layer is effective as a buffer layer to obtain Y 2 Bi 2.5 Fe 5 O 12 , x = 2.5, on glass substrates 15 .…”

Magneto-optical observation of magnetic flux in patterned MgB2 films

“…Bi:YIG films grown by the MOD method allows us to measure clear MO images without zigzag-shaped magnetic domains as observed in LPE-grown garnet film [7]. Pt mirror layer with a thickness of 100 nm was deposited on the garnet film by a magnetron sputtering method in order to obtain high reflectivity and to avoid scattering of the light due to the pattern fabricated on the sample.…”

“…In addition, quantitative MO imaging allows us to obtain current distributions in the superconductors. In order to realize quantitative MO imaging with highresolution and sensitivity, we have developed an MO microscope using polarization modulation technique [5] and MO indicator garnet films by metal-organic decomposition (MOD) method [6,7]. In this paper, we report on quantitative MO imaging of high quality MgB 2 thin films grown by a molecular beam epitaxy (MBE) method.…”

Flux pinning characteristics of superconducting Nb films with asymmetric artificial pinning centers introduced by microfabrication

“…The MO imaging method has a much higher spatial and temporal resolution. Using the MO imaging method, not only the motion of the magnetic flux but also the distribution of the magnetic flux density in superconductors can be directly observed from the bright and dark patterns of the magnetic domain of a garnet film by using a polarizing light microscope [13]. From the asymmetry of the distribution, the intensity of the bulk pinning force along different directions of the applied current can be estimated.…”