Nonlinear Excitations in Low-Dimensional Magnets

这个项目将研究低维磁体中的非线性激励。在低维磁系统中，在磁有序开始时，相关长度随着临界温度的升高而增加。在这个相关长度有限的温度区域，非线性局域激发（孤子）在层状锰体系中已经被实验观察到。进一步观察到，通过温度相关的电子自旋共振线宽观察到，这些激发对自旋相关提供了主要贡献。此外，还观察到一种新型的小孤子被钉在磁空位上。在拟议的研究中，将通过共振技术来研究孤子，以更好地理解层状系统中的磁有序过程。两个主要的重点将包括离散晶格效应和孤子中的量子效应的研究。通常，孤子计算是使用连续近似来完成的，它忽略了离散晶格。然而，由于这种近似在部分感兴趣的温度区域不再有效，离散晶格上的孤子结构将被确定。空位钉住小孤子的量子性质也将被研究。这将通过在晶格中引入高量子磁性杂质（如铜）的实验来实现。这个项目将在教育领域产生广泛的影响。研究生将做大部分的实验研究，而离散晶格理论非常适合本科生的研究。所有要研究的体系都是层状锰化合物，这是一类已经观察到巨磁电阻（GMR）的化合物。对于潜在的器件应用，了解这些层状结构中的磁有序过程是至关重要的。

9974273DrumhellerThis project will investigate nonlinear excitations in low-dimensional magnets. During the onset of magnetic ordering in lower-dimensional magnetic systems, the correlation length increases as the critical temperature is approached from above. In this temperature region where the correlation length is finite, nonlinear localized excitations (solitons) have been experimentally observed in layered manganese systems. It has further been observed that these excitations provide the dominant contribution to the spin correlations as observed through the temperature-dependent electron spin resonance linewidth. In addition, a new type of small soliton pinned to a magnetic vacancy has also been observed. In the proposed research, solitons will be studied through resonance techniques to better understand the magnetic ordering process in layered systems. Two main thrusts will include an investigation of discrete lattice effects, and quantum effects in solitons. Usually, soliton calculations are done using the continuum approximation, which ignores the discrete lattice. However, because this approximation is no longer valid in part of the temperature region of interest, the soliton structure on the discrete lattice will be determined. The quantum nature of the vacancy-pinned small soliton will also be studied. This will be done experimentally through the introduction of a highly quantum magnetic impurity, such as copper, into the lattice.This project will have a broad impact in the area of education. A graduate student will do a large part of the experimental research, and the discrete lattice theory is well suited to undergraduate research. All of the systems to be studied are layered manganese compounds, a class of compounds for which giant magnetoresistance (GMR) has been observed. For potential device applications, it is crucial to have knowledge of the magnetic ordering process in these layered structures.