Masaaki Imamura

Analysis of magnetic fields due to three-phase bus bar currents for the design of an optical current transformer

The dc and ac magnetic fields due to transmission currents flowing through bus bars arranged side-by-side are analyzed to design the three-phase optical current transformer. The structure of optical current transformer with a double core for magnetic shielding is proposed based on the analysis of the interference effect of magnetic fields originated in the three-phase transmission currents and those of the eddy current fields induced by the component of three-phase ac fluxes perpendicular to the wide flat face of plate-form bus bar. It is shown that when a value of 100 is assumed as a relative permeability for the inner shield-core, the eddy current fields which hinder the exact measurement of transmission currents can be decreased by less than 1/10 in the space between the inner core and the outer one, where the magneto-optical field sensor is arranged.

Magneto-optical properties of CdMnTe films on quartz glass and sapphire substrates in the transparent, visible region

Magneto-optical properties in the visible wavelength region are studied on CdMnTe films grown on quartz glass and sapphire (0001) single crystal substrates by MBE. Good quality films with sharp spectra of X-ray diffraction are obtained on the sapphire substrates polished carefully and pre-heated up to 950/spl deg/C. Weak (111) film-growth is observed for films deposited on the quartz glass substrates. A value of Faraday rotation angle of -0.31 deg/cmG at 700 nm is measured in the Cd/sub 0.59/Mn/sub 0.41/Te film grown on the sapphire substrate. The values for the films on the quartz glass substrates are 1/3 of those on sapphire. It is shown that the specific rotation in CdMnTe depends strongly upon the crystalline quality of films deposited on the substrate. >

Temperature dependence of the Faraday rotation for CdMnCoTe films

The temperature dependence of magneto-optical property in the visible wavelength region has been studied on four-element semimagnetic semiconductor CdMnCoTe films deposited on quartz glass substrates by using MBE equipment. A large dispersion of Faraday rotation was observed, and the peak of the Faraday rotation was shifted to the higher photon energies with increasing Mn concentration at low temperatures. At 180 K, the value of the Faraday rotation observed for the Cd0.647Mn0.34Co0.013Te film on quartz glass was −0.36 deg/cmG at 630 nm. It is equivalent to the value of −0.36 deg/cmG observed at 77 K for the Cd0.52Mn0.48Te film on quartz glass. At 77 K, the Faraday rotation observed for the Cd0.647Mn0.34Co0.013Te film on quartz glass was −0.49 deg/cmG at 610 nm. The value is approximately two times larger than that of the Cd0.52Mn0.48Te film deposited on the same quartz glass substrate. The origin of the enhancement of Faraday rotation in CdMnCoTe films has been discussed in terms of the magnetic suscepti...

Magneto-Optical Properties of ZnMnTe Films Grown on Sapphire Substrates

This paper succesively reports the magneto-optical characteristics of ZnMnTe films epitaxially grown on sapphire substrates by MBE, after studying magneto-optical properties observed in the films deposited on quartz glass. The Faraday rotation spectra of Zn(1-x)Mn(x)Te films changed little with Mn concentration, and also the intensity increase of the spectra, which has been reported so far in CdMnTe films grown on (0001) sapphire (SA), was not observed in the films grown on SA. The negative peak of the Faraday rotation in Zn(1-x)Mn(x)Te films that have an absorption edge at 520-530 nm is near the edge. The results suggest that Zn(1-x)Mn(x)Te films are useful for green lights.

Magneto-optical properties of wider gap II-VI ZnMnTe and ZnMnCoTe films

In CdMnTe and CdMnCoTe films, Mn shifts the absorption edge toward higher energies. However, this gap shift occurs at around 2.1eV because the band gap of the combination of CdTe (1.53eV) and wideband gap MnTe (2.9eV) is small. In order to widen the gap of AII1−xMnxBVI alloys and effectively use LDs that work at shorter wavelengths for Faraday rotation, we have studied ZnMnTe and ZnMnCoTe films, whose parent materials are wideband gap ZnTe (2.28eV) and MnTe. The relationship between the quantity (αhν)2 and the optical energy for Cd0.65Mn0.35Te and data on Zn0.75Mn0.25Te and Zn0.79Mn0.20Co0.01Te films showed that the direct gap energy of the Cd0.65Mn0.35Te film is roughly 2.25eV and the gap of Zn0.75Mn0.25Te and Zn0.79Mn0.20Co0.01Te (∼2.4eV) is 0.15eV (∼40nm) larger than that of Cd0.65Mn0.35Te. The increase is due to the combination of wideband gap ZnTe and MnTe. Transparency and Faraday rotation are observed for Zn1−xMnxTe and Zn1−x−yMnxCoyTe films.

The Status of Domain Theory for an Investigation of Magnetostriction and Magnetization Processes in Grain-Oriented Si-Fe Sheets

Magnetostriction in modern (110)[001] grain-oriented Si-Fe sheets can be understood by considering magnetic domain structures and their variation with magnetization on the basis of magnetic domain theory. Magnetostrictive elongation in g.o. sheets is dominated by the behavior of 90? domain walls included in subdomains which appear in the main domains carrying the magnetization of the [001] direction. The relationship among magnetostriction, the static domain structure and process of magnetization is reviewed with respect to g.o. sheets with conventional thickness and ones with extremely reduced thickness. Losses are reviewed in relation to the domain structure and its variation during magnetization.

Magnetooptical properties of diluted magnetic semiconductor CdMnCoTe films

The relationship between Faraday rotation /spl theta//sub F/ and magnetic field H in the visible wavelength region for films of the diluted magnetic semiconductor CdMnCoTe deposited on quartz glass substrates by molecular beam epitaxy is examined. The magnitude of /spl theta//sub F/ in the CdMnCoTe films is compared with that in CdMnTe film and ferrimagnetic garnet Bi:YIG film, and it is shown that the Faraday rotation for Cd/sub 0.51/Mn/sub 0.414/Co/sub 0.076/Te film is approximately three times that for Cd/sub 0.39/Mn/sub 0.61/Te film. The value of /spl theta//sub F/ in the Cd/sub 0.51/Mn/sub 0.414/Co/sub 0.076/Te film at an optical wavelength of 670 nm was -0.2/spl deg///spl mu/m under a magnetic field of 6.8 kOe. The relationship between the values of /spl theta//sub F/ for the diluted magnetic semiconductor films and the substrate materials is also discussed.

Evaluation of Faraday-rotation characteristics with CdMnCoTe and CdMnFeTe films

Magneto-optical properties with quaternary CdMnCoTe and CdMnFeTe films deposited on quartz glass substrates using molecular beam epitaxy equipment are studied at an optical wavelength of 635 nm. The magnitude of the Faraday rotation θF in the CdMnCoTe films was compared with that in the CdMnFeTe films, and the largest θF has been obtained for the Cd0.603Mn0.371Co0.026Te film. It is shown that a large θF was also observed in the Cd0.575Mn0.372Fe0.053Te film and its optical properties were poor compared to those in the Cd0.603Mn0.371Co0.026Te film. A few problems that occur for measurements of the Faraday rotation are indicated.Magneto-optical properties with quaternary CdMnCoTe and CdMnFeTe films deposited on quartz glass substrates using molecular beam epitaxy equipment are studied at an optical wavelength of 635 nm. The magnitude of the Faraday rotation θF in the CdMnCoTe films was compared with that in the CdMnFeTe films, and the largest θF has been obtained for the Cd0.603Mn0.371Co0.026Te film. It is shown that a large θF was also observed in the Cd0.575Mn0.372Fe0.053Te film and its optical properties were poor compared to those in the Cd0.603Mn0.371Co0.026Te film. A few problems that occur for measurements of the Faraday rotation are indicated.

Faraday rotation in quaternary CdMnCoTe thick films deposited on transparent quartz glass substrates

In this paper, we investigate the Faraday rotation of thick diluted magnetic semiconductor CdMnCoTe films deposited on relatively thin quartz glass substrate from the viewpoint of practical application. Magnetization curve for CdMnCoTe film measured using vibrating sample magnetometer at room temperature.

Extremely low frequency losses and thermal fluctuation after effect in soft ferrites

Magnetic losses in soft magnetic ferrites have been measured at extremely low frequencies and high magnetic inductions. A logarithmic variation of losses per cycle with frequency has been found in a frequency range between 0.01 Hz and less than 100 Hz. This anomalous loss with frequency dependence is attributed to the thermal fluctuation after effect which yields the same anomalous losses in metallic soft magnetic materials. The after effect constant Sv has been calculated from this anomalous loss and the static and eddy current losses in soft ferrites have been discussed.