| Co-Investigator(Kenkyū-buntansha) |
MIYAZAKI Yuzuru TOHOKU UNIVERSITY,School of Engineering, Research Associate, 大学院・工学研究科, 助手 (40261606)
ONO Yasuhiro TOHOKU UNIVERSITY,School of Engineering, Research Associate, 大学院・工学研究科, 助手 (30211832)
SHAMOTO Shin-ichi TOHOKU UNIVERSITY,School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (90235698)
ITO Tadashi TOHOKU UNIVERSITY,School of Engineering, Professor, 大学院・工学研究科, 教授 (60004503)
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| Research Abstract |
Present study was aimed to obtain structural characteristics of optically sennsitive magnetic clusters and its related physical properties of magnetic clusters in the II-VI-type semiconductors deped with magnetic metal atoms. Single crystals of Zn_<1-x>Mn_xTe with x=0.3-0.6 were prepared by the standard Bridgeman method. Structural study on the average lattice was done by means of powder x-ray diffraction measurement in the temperature range from 20K to the ambient. Magnetic susceptibility measurements were performed by means of SQUID manetometer in the range from the ambient to 4.2K.The spin glass temperatures, Tg, were determined accordingly. In the course of the present study, diffuse intensities due to the short range magnetic ordering was found by the powder neutron diffraction measurement below 100K.The magnetic structure-type of the magnetic clusters, which is responsible for the diffuse scatterings, has been determined by means of single crystal neutron diffraction study. The s
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ingle crystal neutron diffraction measurement was performed in the magnetic field up to 5-Tesla by the use of high resolution neutron diffractometers, HRPD and HERMES installed in the JRR3M reactor hall and the thermal guide hall, respectively. Two dimensional neutron diffraction intensity measurement was performed in the 001 reciprocal plane simultaneously by many neutron counters set in the instruments. Brillouin scattering measurement was tried to study the spin dynamics in the low temperature range. Brillouin scattering measurement, i.e., an optical inelastic scattering measurement, is suitable to measure the excitation levels in the range below 0.5meV with the resolution of 0.01meV.A new Ar-gas laser was purchased with the aid of present financial support and a 5-pass high resolution Fabry-Perot interferrometer was made from an old 3-pass interferrometer, and then a 5-pass Brillouin scattering system was assembled. Brillouin scattering measurement at low temperatures in the magnetic field up to 4000 Oe was successfully performed for the complicated ferromagnetic metallic compound. A part of the magnon dispersion relationship consistent with the neutron scattering data was determined by this instrument. Neutron inelastic scattering measurement has been performed for Zn_<0.6>Mn_<0.4>Te sample using the cold neutron spectrometer AGNES.Critical scattering, associated with the spin glass transition has been observed for the first time in this semimagnetic semiconductor. The critical scattering was observed at temperatures in the vicinity of the spin glass transition temperature, 17K.Photo conductivity has been found also for the first time below 150K in Zn_<0.6>Mn_<0.4>Te sample. The electric AC conductivity has been increased dramaticaly under the laser light with the wave lengths of lambda=6328,5145 and 4880A,respectively. The conductivity was reduced to the original level after the light was darkened, but it took very long, i.e.2000 second at 50K,being above the Less
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