Photoinduced Magnetic Effect in Magnetic Oxides

钇铁石榴石样品冷却到77 K后升温，用白色光照射，在130 K附近同时观察到两种类型的μ_1（t），即低温下不可逆的降低和可逆的失稳（DA）。在加热先前照射的样品时，观察到磁导率μ * 的虚部的三重峰作为温度的函数。此外，观察到mu* 的每个峰取决于照射时间。最低温度峰称为P_I，中间温度峰称为P_I<II>，最高温度峰称为P_I<III>。由各峰频率的Arrhenius图求得活化能分别为0.095-0.22eV（P_1），0.50eV（P_2）<II>和0.81eV（<III>P_3）。接下来，已经研究了mu* 的热变化作为光强度l（时间作为强度的量度）的函数。这一现象可以用一维氧空位模型来解释，氧空位形成基态和三个亚稳激发能级，在亚稳激发能级中，受激电子可以通过通常所说的激发能级自发地进入这些能级。假设每个亚稳能级有两个磁等效势，它们被激活能U_<exc1>，U_<exc2>和U_分开，激活能U_和U<exc3>_分别与P_I，P_<II>和P_有关<III>。这些水平可能与“近”、“中“和/或“远”地点有关。为了解释这些峰的相关性，我们假设一组连续方程。

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.