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Photoinduced Phase Transitions and their Dynamics

光致相变及其动力学

基本信息

批准号：
11215207
负责人：
SAKAI Osamu
金额：
$ 9.54万
依托单位：
Tokyo Metropolitan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11215207/
关键词：
Photo-induced low-spin high-spin transition incubation time nucleation process volume striction Monte Carlo simulation magnetic polaron low density carrier FLAPW band calculation 光誘起low-spin high-spin転移格子緩和ピン止め光誘起high-spin low-spi

项目摘要

We studied mainly following three subjects :1) Monte-Carlo simulation Study on domain formation in photo-induced transition : [Fe(2-pic)_3]Cl_3EtOH shows cooperative low-spin (LS) to high-spin (HS) states transition when the light is irradiated to the LS phase. We studied theoretically these phenomena by Monte Carlo and the analytic methods. It was shown that the fluctuation due to the repetition of the excitation by light and de-excitation process acts as the driving force to surmount the barrier of domain nucleation. To explain the macroscopic phase separation, a model including the coupling with volume striction mode was introduced. The sharp step-like conversion was ascribed to the de-pinning effect of the volume striction.2) Magnetic semiconductors : The ferromagnetism induced by the low density carrier which is doped by optical or chemical methods was studied by both Monte Carlo and the analytic methods. The role of magnetic polaron effect in the magnetism and the optical process was analyzed.3) Electronic band structure of Kco[Fe(CN)_6][16] : To clarify the electronic structures of the photo-induced ferrimagnetic state, the LDA band calculations on the basis of the FLAPW method was carried out. The energy of Co-d γ band decreases and locates very near the Fermi energy, and thus electron transfers from Fe ion site state to Co site in the excited state.

主要研究了以下三个方面的内容：1)光诱导相变中磁畴形成的蒙特卡罗模拟研究：[Fe(2-pic)_3]Cl3EtOH在光照射到LS相时，表现出协同的低自旋(LS)到高自旋(HS)态的转变。我们用蒙特卡罗方法和解析方法对这些现象进行了理论研究。结果表明，光激发和去激发过程的重复引起的涨落是跨越磁畴形核障碍的驱动力。为了解释宏观相分离，引入了一个包含体积限制模耦合的模型。2)磁性半导体：用蒙特卡罗方法和解析方法研究了低密度载流子的光学或化学掺杂引起的铁磁性。分析了磁极化子效应在磁性和光学过程中的作用。3)KCo[Fe(CN)_6][16]的电子能带结构：为了阐明光生亚铁磁态的电子结构，在FLAPW方法的基础上进行了LDA能带计算。Co-dγ能带能量降低，位于费米能级附近，电子在激发态从Fe离子格态转移到Co格位。