US-Federal Republic of Germany Cooperative Research: Thermodynamics and Short-Range Order in Amorphous Rare Earth - Transition Metal Alloys

该奖项支持加州大学圣地亚哥分校的Frances Hellman教授与德意志联邦共和国哥廷根大学金属物理研究所的Ruediger Bormann博士的合作研究。他们感兴趣的是由稀土和过渡金属元素衍生的铁磁性非晶金属合金。这些合金的薄膜具有很大的单轴磁各向异性，这可能是由生长过程在短时间内引起的。相对于这些薄膜的晶相，某些热力学函数控制着非晶相的稳定性。这些研究人员将制备几种合金的薄膜样品，这些合金的成分或沉积温度各不相同。他们将进行广泛的热力学测量（在德国），结合磁性和结构表征（在加利福尼亚），以比较短程有序的程度和类型。Hellman博士的背景是薄膜比热测量、非晶稀土过渡金属合金的制备、磁性和结构表征。她的德国合作者基于非晶材料（包括薄膜）的某些热力学性质的测量，在计算非晶和晶体相自由能方面有着独特而丰富的经验。他们还拥有超高真空磁控溅射系统，专门用于制备高纯度非晶金属合金，特别是那些含有磁性元素的合金。非晶磁性材料的中、短程有序及其与磁各向异性的关系是一个具有基础和技术意义的问题。在非晶薄膜中进行热力学测量的困难阻碍了材料科学领域的进展。这项工作将有助于解决非晶薄膜中磁性各向异性的起源问题。它还将有助于确定导致某些合金相分离的条件，这些合金是有前途的磁存储材料。

This award supports Professor Frances Hellman, University of California at San Diego, for collaborative research with Dr. Ruediger Bormann of the Institute of Metal Physics, University of Goettingen, Federal Republic of Germany. They are interested in ferri-magnetic amorphous metal alloys derived from rare earth and transition metal elements. Thin films of these alloys possess a large, poorly-understood uni- axial magnetic anisotropy, which may be induced in the short-range order by the growth process. Certain thermodynamic functions control the stability of the amorphous phase relative to the crystalline phases of these thin films. These investigators will prepare thin film samples of several alloys, differing in composition or deposition temperature. They will make extensive thermodynamic measurements (in Germany), in conjunction with magnetic and structural characterization (in California), in order to compare the degree and type of short range order. Dr. Hellman's background is in thin film specific heat measurement and in preparation and magnetic and structural characterization of amorphous rare earth-transition metal alloys. Her German collaborators have unique and extensive experience in calculations of amorphous and crystalline phase free energies, based on measurements of certain thermodynamic properties of amorphous materials (including thin films.) They also have an ultra-high vacuum magnetron sputtering system, dedicated to preparation of high purity amorphous metallic alloys, especially those containing magnetic elements. The question of intermediate and short range order in amorphous magnetic materials and their relationship to the magnetic anisotropy is of basic as well as technological interest. The difficulty of making thermodynamic measurements in amorphous thin films has delayed progress in this area of materials science. This work should contribute to resolving the question of the origin of magnetic anisotropy in amorphous films. It will also help determine the conditions leading to phase separation in certain alloys which are promising magnetic storage materials.