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Synthesis and Orbital structure of structure- and valence-controlled layered manganites

结构和价态控制的层状锰酸盐的合成和轨道结构

基本信息

批准号：
10440091
负责人：
NAKAMURA Arao
金额：
$ 9.73万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

We have systematically investigated electric, magnetic and optical properties of structure- and valencecontrolled manganites which show photoinduced magnetic transitions. The following is a major result.1. The temperature variations of the resistivity and specific heat have been measured for prototypical half-metallic ferromagnets R_<0.6>Sr_<0.4>MnO_3 by controlling the one-electron band width. We have observed the T^3 dependence of the resistivity which is interpreted in terms of the anomalous single-magnon scattering process in the half-metallic system.2. Photoinduced spin disorder and its dynamical behavior have been investigated for La_<0.7>Ca_<0.3>MnO_3. By optical injection of down-spin electrons into the Mn e_g orbital the spin disorder in the ferromagnetic phase is induced. We have found that the recovery time to the spin ordered state is lengthened from 30 ns at 5 K to 30 μs when the temperature approaches to the critical temperature of the phase transition. This result clearly demonstrates the critical slowing down of relaxation time in the phase transition.3. Photoinduced resistivity change in a La_<0.6>Ca_<0.4>MnO_3 film has been investigated with variation of the excitation photon energy and temperature. The magnitude of the photoinduced resistivity change steeply decreases with increasing temperature above the transition temperature of 315 K.Since the photoinduced signal is enhanced by injection of the down spin carriers, the resistivity change is ascribed to the photoinduced spin disorder in the ferromagnetic metallic state. This result indicates that one can detect photoinduced spin disorder with the resistivity signal.

我们系统地研究了结构和价态控制的亚锰酸盐的电、磁和光学特性，这些特性显示出光致磁转变。主要结果如下： 1．通过控制单电子带宽，测量了原型半金属铁磁体R_<0.6>Sr_<0.4>MnO_3的电阻率和比热的温度变化。我们观察到电阻率与T^3的相关性，这可以用半金属系统中的反常单磁振子散射过程来解释。2．研究了La_<0.7>Ca_<0.3>MnO_3的光致自旋紊乱及其动力学行为。通过将自旋电子光学注入 Mn e_g 轨道，引起铁磁相中的自旋无序。我们发现，当温度接近相变临界温度时，自旋有序态的恢复时间从 5 K 时的 30 ns 延长到 30 μs。这一结果清楚地表明了相变中弛豫时间的显着减慢。3．研究了La_<0.6>Ca_<0.4>MnO_3薄膜中光致电阻率随激发光子能量和温度变化的变化。当温度高于 315 K 的转变温度时，光致电阻率变化的幅度急剧减小。由于光致信号通过向下自旋载流子的注入而增强，因此电阻率变化归因于铁磁金属态中的光致自旋无序。这一结果表明可以利用电阻率信号检测光致自旋无序。