Nonlinear Excitations in Low-Dimensional Magnets

9974273Drumheller本项目将研究低维磁体中的非线性激励。 在低维磁系统中，当从上面接近临界温度时，关联长度增加。 在这个温度范围内，相关长度是有限的，非线性局域激发（孤子）已被实验观察到层状锰系统。 进一步观察到，这些激发提供了通过温度依赖的电子自旋共振线宽观察到的自旋相关性的主要贡献。 此外，还观察到了钉扎在磁空位上的新型小孤子。 在拟议的研究中，将通过共振技术研究孤子，以更好地理解分层系统中的磁有序过程。 两个主要的推动力将包括离散晶格效应的调查，和孤子的量子效应。 通常，孤子计算是使用连续近似，忽略了离散晶格。 然而，由于这种近似在感兴趣的温度区域的一部分不再有效，离散晶格上的孤子结构将被确定。 我们也将研究空位钉扎小孤子的量子性质。 这将通过在晶格中引入高量子磁性杂质（如铜）来进行实验，该项目将在教育领域产生广泛影响。 一个研究生将做很大一部分的实验研究，离散格理论非常适合本科生的研究。 所有待研究的系统都是层状锰化合物，这是一类已经观察到巨磁电阻（GMR）的化合物。 对于潜在的设备应用，这是至关重要的，有这些层状结构中的磁有序过程的知识。

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 However, because this approximation is no longer valid in part of the temperature region of interest, the soliton structure on the discrete lattice will be determined.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.