Two-phase coexistence region in mechanically alloyed Cu-Fe: An X-ray absorption near-edge structure study

Extended X-ray absorption fine structure has been used to determine a crystallographic distortion in the Co layers in Co-Cu single-crystal superlattices grown on Cu(100). The FCC structure of the superlattice imposed by the Cu substrate is distorted along the growing direction for the Co layers, which are compressed perpendicularly to the interfaces. They adopt the in-plane lattice constant of the Cu substrate, keeping constant the atomic volume of Co (11.30 AA3/atom), close to the value for HCP-Co.

The structural characterization of Co-Cu(100) superlattices by X-ray absorption spectroscopy

The development of the capability to engineer the surface properties of materials to match specific requirements demands high quality surface characterization techniques. The ideal tool should provide chemically specific structural characterization as well as surface sensitivity and depth profiling. Ideally the characterization method should also be applicable to systems both with and without long range order. X-ray absorption spectroscopy fine structure, when using the standard transmission detection system, provides all this information with the significant exception of surface sensitivity. In contrast, by detecting the reflected instead of the transmitted beam, it encompasses all these requirements because when the incident beam impinges onto a sample surface at glancing angles, in conditions close to the total reflection, only the outermost regions of the system under study are sampled. Such a technique provides information about the local structure as a function of depth as well as thin layer structure in the case of layered samples. Although it is potentially the ideal tool to study surface modified materials, experimental difficulties have hampered its widespread use in the fields of surface and materials sciences. As a solution to the experimental challenges, we provide a detailed description of an appropriate experimental station, the sample requirements, the measuring protocols, and software routines needed to optimize the collection of the data. To illustrate the capabilities of the technique the results obtained for a model multilayer sample are presented and analyzed under the total external reflection approximation.

Optimized end station and operating protocols for reflection extended x-ray absorption fine structure (ReflEXAFS) investigations of surface structure at the European Synchrotron Radiation Facility beamline BM29.

Fe75Zr25/Cu64Zr36 amorphous multilayers were prepared by magnetron sputtering. Atom probe tomography was employed to analyze the atomic inter-diffusion at the interface of the multilayers before and after annealing (573 K, 60 min). An unexpected enhanced inter-diffusion of the immiscible elements Fe and Cu was detected at the interface of the multilayers. As the inter-diffusion in amorphous multilayers is much faster than that in the crystalline counterparts, this process may open a way to manipulate or create amorphous multilayers with new properties. This idea agrees with the observation of the variation of magnetic properties of Fe75Zr25/Cu64Zr36 amorphous multilayers.

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Enhanced inter-diffusion of immiscible elements Fe/Cu at the interface of FeZr/CuZr amorphous multilayers

Couplings and interface effects on magnetic and electronic properties in binary Ni/Cu superlattices

The structure and magnetic properties of Fe/Cu multilayered films with a constant total Fe thickness of 1050 A but varying Fe-layer thickness from 6.3 to 42 A and varying Cu to Fe thickness ratio from 1 to 3 were investigated using x-ray diffraction (XRD), x-ray absorption fine-structure (XAFS) spectroscopy, and magnetic measurements. Samples were prepared at room temperature on mica, glass, and silicon substrates using the dc-magnetron-sputtering method. For films with the same Fe-layer thickness, it was found that the magnetic moment of Fe decreases with increasing thickness ratio of Cu to Fe. For films with a Cu to Fe thickness ratio of 3, it was found that the magnetic moment of Fe decreases with decreasing thickness of the individual Fe layers. XRD and XAFS results revealed that in the multilayered films, Cu has a well-defined fcc structure with minimal amount of structural disorder independent of the individual layer thickness or thickness ratio. On the other hand, quantitative analysis of EXAFS data revealed that the crystal structure of Fe changes with decreasing thickness of the Fe layers from distorted bcc (for 42- and 21-A-thick Fe layers) to fcc (for 10.5- and 6.3-A-thick Fe layers) in films with the Cu layermore » three times thicker than the Fe layer. The single-phase fcc Fe of the 6.3-A Fe/19-A Cu multilayered film was found to have a lattice constant of 3.596 A and is ferromagnetic with a Curie temperature of 210 K and a spontaneous magnetization of [similar to]690 emu/cm[sup 3].« less

J. P. Teter

Papers

Structure and magnetic properties of magnetron-sputtered Fe/Cu multilayered thin films.