| Co-Investigator(Kenkyū-buntansha) |
MATSUBARA Ikuya Kanagawa Dental College, Dept. Denstry, Research Associate, 歯学部, 助手 (40157342)
MAEDA Keiitirou Kanagawa Dental College, Dept. Denstry, Associated Professor, 歯学部, 助教授 (10084766)
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| Research Abstract |
Warming a sample of yttrium iron garnet after cooled to 77 K and illuminated with white light, the two types of mu_1(t) were simultaneously observed around 130 K ; an irreversible decrease so long as kept at low temperature and a reversible type or disaccommodation (DA). On warming the previously illuminated sample, the triple peaks of the imaginary part of permeability mu* were observed as a function of temperature. Furthermore, it was observed that each peak of mu* depends on the illuminating time. The lowest temperature peak is termed P_I, the intermediate temperature peak P_<II> and the highest temperature peak, P_<III>. From the Arrehnius plot of the frequency associated with each peak, the activation energies are obtained as 0.095-0.22eV for P_I, 0.5OeV for P_<II> and 0.81 eV for P_<III>, respectively. Next, a thermal variation of mu* has been studied as a function of light intensity l (time as a measure of intensity). The observation may be exphdned in terms of the one dimensional model of an oxygen vacancy which forms a ground state and three metastable excited levels In which an excited electron may spontaneously go to these levels via usually termed excited' level. Each of these metastable levels is assumed to have two magnetically equivalent potentials separated by barriers of activation energies U_<exc1>, U_<exc2> and U_<exc3> which are associated with P_I, P_<II> and P_<III>, respectively. These levels could be associated with "near", " intermediate " and or "far" site. In order to explain the dependence of these peaks we postulate a set of consecutive equations.
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