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arXiv cond-mat/0103471cond-mat.str-el
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对角无序双交换模型的动力学平均场论

Dynamical mean-field theory of a double-exchange model with diagonal disorder

B. M. Letfulov, J. K. Freericks

摘要:

通过精确求解双交换模型(具有类伊辛局域自旋)和动力学平均场论中的猝灭二元无序,提出了一个简化的掺杂锰氧化物巨磁电阻模型.我们研究的磁性和电和热输运。我们的解说明了三种不同的物理机制:(i)弱无序机制,系统表现为重正化双交换系统(这是不足以描述的行为在锰氧化物);(ii)强无序制度,其中该系统是由强耦合物理描述的绝缘相(这是最有利的大磁阻);和(iii)一个过渡区的中度无序,其中双交换和强耦合效应是重要的。我们使用的热电势作为一个严格的测试,这个模型的适用性锰氧化物,发现该模型是无法正确地解释实验中看到的热电势的符号变化。

英文摘要:

We present a simplified model for the colossal magnetoresistance in doped manganites by exactly solving a double-exchange model (with Ising-like local spins) and quenched binary disorder within dynamical mean field theory. We examine the magnetic properties and the electrical and thermal transport. Our solution illustrates three different physical regimes: (i) a weak-disorder regime, where the system acts like a renormalized double-exchange system (which is insufficient to describe the behavior in the manganites); (ii) a strong-disorder regime, where the system is described by strong-coupling physics about an insulating phase (which is the most favorable for large magnetoresistance); and (iii) a transition region of moderate disorder, where both double-exchange and strong-coupling effects are important. We use the thermopower as a stringent test for the applicability of this model to the manganites and find that the model is unable to properly account for the sign change of the thermopower seen in experiment.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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