Experimental Studies of Condensed Magnetic Systems

利用交流磁化率X′(w)和中子自旋回波技术，对随机交换（REIM）和随机场（RFIM） Ising模型项中最近发现的异常动态临界行为进行了广泛的研究。将研究线性Xl(w)和非线性X'nl (w)作为w的函数。RFIM的静态临界指数的更精确值将从中子散射实验中寻求。将制造和探索新颖的、磁密度高的RFIM系统，希望利用双折射和电容技术找到一个纯Ising到RFIM交叉行为的例子。一种新的光学吸收方法将用于更好地理解非平衡场冷RFIM态的畴结构性质。在理想的Ising体系ironxzinc1-xfluorine2中，REIM/RFIM与Ising自旋玻璃的交叉行为将在渗流阈值附近进行研究。最后，他们将继续利用AFMR、数字间电容、FTIR、光谱学和中子散射技术制备和研究氟铁2/氟锌2、氟锰2/氟锌2和氟铁2/氟钴2的外延反铁磁绝缘体和超晶格。他们希望观察到驻自旋波和新的不稳定模式、维数交叉、布里渊区的折叠和态的磁振子密度的改变。这些综合研究应该为磁现象研究的前沿领域提供有价值的见解。

An extensive investigation is proposed of the recently uncovered unusual dynamic critical behavior in random exchange (REIM) and random field (RFIM) Ising model terms, using ac susceptibility X'(w) and neutron spin echo techniques. Both linear Xl(w) and nonlinear X'nl (w) will be investigated as a function of w. More precise values for the static critical exponents of the RFIM will be sought from neutron scattering experiments. Novel, magnetically dense, RFIM systems will be fabricated and probed in the hope of finding an example of pure Ising to RFIM crossover behavior, using birefringence and capacitance techniques. A new optical absorption method will be used to better understand the nature of the domain structure of the nonequilibrium, field- cooled RFIM state. The crossover form REIM/RFIM to Ising spin- glass behavior will be examined near the percolation threshold in the ideal Ising system ironxzinc1-xfluorine2. Lastly, they will continue the preparation and study of epitaxed antiferromagnetic insulators and superlattices of iron fluorine2/zinc fluorine2, manganese fluorine2/zinc fluorine2 and iron fluorine2/cobalt fluorine2 using AFMR, interdigital capacitance, FTIR and optical spectroscopy and neutron scattering techniques. They hope to observe standing spin wave and new instability modes, dimensionality crossover, folding of the Brillouin Zone and modification of the magnon density of states. These combined studies should provide valuable insights in areas at the forefront of research in magnetic phenomena.