Fallarino Lorenzo, Riego Patricia, Kirby Brian J, Miller Casey W, Berger Andreas
CIC nanoGUNE, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian, Spain.
Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, 01328 Dresden, Germany.
Materials (Basel). 2018 Feb 6;11(2):251. doi: 10.3390/ma11020251.
: Ferromagnetic alloy materials with designed composition depth profiles provide an efficient route for the control of magnetism at the nanometer length scale. In this regard, cobalt-chromium and cobalt-ruthenium alloys constitute powerful model systems. They exhibit easy-to-tune magnetic properties such as saturation magnetization and Curie temperature while preserving their crystalline structure over a wide composition range. In order to demonstrate this materials design potential, we have grown a series of graded Co₁Cr and Co₁Ru (1010) epitaxial thin films, with and following predefined concentration profiles. Structural analysis measurements verify the epitaxial nature and crystallographic quality of our entire sample sets, which were designed to exhibit in-plane -axis orientation and thus a magnetic in-plane easy axis to achieve suppression of magnetostatic domain generation. Temperature and field-dependent magnetic depth profiles have been measured by means of polarized neutron reflectometry. In both investigated structures, and are found to vary as a function of depth in accordance with the predefined compositional depth profiles. Our Co₁Ru sample structures, which exhibit very steep material gradients, allow us to determine the localization limit for compositionally graded materials, which we find to be of the order of 1 nm. The Co₁Cr systems show the expected U-shaped and depth profiles, for which these specific samples were designed. The corresponding temperature dependent magnetization profile is then utilized to control the coupling along the film depth, which even allows for a sharp onset of decoupling of top and bottom sample parts at elevated temperatures.
具有设计成分深度分布的铁磁合金材料为在纳米长度尺度上控制磁性提供了一条有效途径。在这方面，钴铬合金和钴钌合金构成了强大的模型体系。它们展现出易于调节的磁性，如饱和磁化强度和居里温度，同时在很宽的成分范围内保持其晶体结构。为了证明这种材料设计潜力，我们生长了一系列具有预定义浓度分布的梯度Co₁Cr和Co₁Ru(1010)外延薄膜。结构分析测量验证了我们整个样品集的外延性质和晶体质量，这些样品集被设计为具有面内 - 轴取向，从而具有面内易磁化轴以抑制静磁畴的产生。通过极化中子反射测量法测量了温度和磁场依赖的磁性深度分布。在这两种研究结构中，发现 和 随深度变化，符合预定义的成分深度分布。我们的Co₁Ru样品结构具有非常陡峭的材料梯度，这使我们能够确定成分渐变材料的局域化极限，我们发现其约为1纳米。Co₁Cr体系呈现出预期的U形 和 深度分布，这些特定样品就是为此设计的。然后利用相应的温度依赖磁化分布来控制沿薄膜深度的耦合，这甚至允许在高温下顶部和底部样品部分的解耦急剧开始。
