2 results
Search Results
Now showing 1 - 2 of 2
- ItemHigh field superconducting properties of Ba(Fe1-xCox)2As2 thin films(London : Nature Publishing Group, 2015) Hänisch, Jens; Iida, Kazumasa; Kurth, Fritz; Reich, Elke; Tarantini, Chiara; Jaroszynski, Jan; Förster, Tobias; Fuchs, Günther; Hühne, Ruben; Grinenko, Vadim; Schultz, Ludwig; Holzapfel, BernhardThe film investigated grew phase-pure and highly textured with in-plane and out-of-plane full width at half maximum, FWHM, of = 0.74° and = 0.9°, Suppl. S1. The sample, however, does contain a large density of ab-planar defects, as revealed by transition electron microscope (TEM) images of focused ion beam (FIB) cuts near the microbridges, Fig. 1. These defects are presumably stacking faults (i.e. missing FeAs layers)20. The reason for this defect formation (also observed on technical substrates)21 is not fully understood. Possible reasons are a partial As loss during deposition22, and relaxation processes in combination with the Fe buffer layer23. Estimating the distance between these intergrowths leads to values varying between 5 and 10 nm. Between the planar defects, an orientation contrast is visible in TEM (inset Fig. 1b), i.e. the brighter crystallites are slightly rotated either around (010) (out-of-plane spread, ) or around (001) (in-plane spread, ) and enclosed by dislocation networks or small-angle GBs. Since the crystallites are sandwiched between planar defects, an in-plane misorientation is most likely. The out-of-plane misorientation, on the other hand, is visible as a slight tilt of the ab-planar defects with respect to each other, especially in the upper part of the sample. No globular or columnar precipitates were found.
- ItemHall-plot of the phase diagram for Ba(Fe1−xCox)2As2(London : Nature Publishing Group, 2016) Iida, Kazumasa; Grinenko, Vadim; Kurth, Fritz; Ichinose, Ataru; Tsukada, Ichiro; Ahrens, Eike; Pukenas, Aurimas; Chekhonin, Paul; Skrotzki, Werner; Teresiak, Angelika; Hühne, Ruben; Aswartham, Saicharan; Wurmehl, Sabine; Erbe, Manuela; Hänisch, Jens; Holzapfel, Bernhard; Drechsler, Stefan-Ludwig; Efremov, Dmitri V.The Hall effect is a powerful tool for investigating carrier type and density. For single-band materials, the Hall coefficient is traditionally expressed simply by , where e is the charge of the carrier, and n is the concentration. However, it is well known that in the critical region near a quantum phase transition, as it was demonstrated for cuprates and heavy fermions, the Hall coefficient exhibits strong temperature and doping dependencies, which can not be described by such a simple expression, and the interpretation of the Hall coefficient for Fe-based superconductors is also problematic. Here, we investigate thin films of Ba(Fe1−xCox)2As2 with compressive and tensile in-plane strain in a wide range of Co doping. Such in-plane strain changes the band structure of the compounds, resulting in various shifts of the whole phase diagram as a function of Co doping. We show that the resultant phase diagrams for different strain states can be mapped onto a single phase diagram with the Hall number. This universal plot is attributed to the critical fluctuations in multiband systems near the antiferromagnetic transition, which may suggest a direct link between magnetic and superconducting properties in the BaFe2As2 system.