Nonlinear Excitations in Low-Dimensional Magnets

这个项目将研究低维磁铁中的非线性激发。在低维磁系统的磁有序化开始时，关联长度随温度的升高而增大。在关联长度有限的温度范围内，实验观察到了层状锰系统中的非线性局域激发(孤子)。进一步观察到，通过温度相关的电子自旋共振线宽观察到，这些激发对自旋关联的贡献占主导地位。此外，还观察到了一种钉扎在磁性空位上的新型小孤子。在拟议的研究中，将通过共振技术来研究孤子，以更好地了解层状系统中的磁有序过程。两个主要的推进将包括对离散晶格效应和孤子中的量子效应的研究。通常，孤子计算采用连续介质近似，忽略了离散晶格。然而，由于这种近似在感兴趣的部分温度区域中不再有效，因此将确定离散晶格上的孤子结构。我们还将研究空位钉扎的小孤子的量子性质。这将通过在晶格中引入高量子磁性杂质(如铜)来进行实验。这一项目将在教育领域产生广泛的影响。研究生将做很大一部分实验研究，而离散格子理论非常适合本科生的研究。所有被研究的体系都是层状锰化合物，这类化合物已经观察到巨磁电阻(GMR)。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 However, because this approximation is no longer valid in part of the temperature region of interest, the soliton structure on the discrete lattice will be determined.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.