Experimental Studies of Condensed Magnetic Systems

凝聚磁系统的实验研究

• 批准号: 8815560
• 负责人: Vincent Jaccarino
• 金额: --
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-01-01 至 1992-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8815560&HistoricalAwards=false
• 关键词: Experimental; Studies; Condensed; Magnetic; Systems

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.

利用交流磁化率X‘(W)和中子自旋回波技术，对最近发现的随机交换(Reim)和随机场(RFIM)Ising模型项中的异常动态临界行为进行了广泛的研究。线性XL(W)和非线性X‘nl(W)都将作为w的函数进行研究。RFIM的静态临界指数将从中子散射实验中寻求更精确的值。利用双折射和电容技术，将制造和探索新型的、磁密度高的RFIM系统，以期找到一个纯Ising到RFIM交叉行为的例子。一种新的光吸收方法将被用来更好地理解非平衡、场冷却的RFIM态的磁畴结构的性质。在理想的Ising系统ironxzinc1-xfline2中，我们将在渗流阈值附近研究从Reim/RFIM到Ising自旋玻璃的交叉行为。最后，他们将继续利用AFMR、叉指电容、傅里叶变换红外光谱、光学光谱和中子散射技术来制备和研究氟化铁/氟化锌、氟化锰/氟化锌和氟化铁/氟钴等外延反铁磁性绝缘体和超晶格。他们希望观察到驻留的自旋波和新的不稳定模、维度交叉、布里渊区的折叠和磁振子态密度的修正。这些综合研究应该在磁现象研究的前沿领域提供有价值的见解。