Atomic ordering of ferromagnetic alloys, such as Heusler compounds, vastly influences their magnetic properties and overall usability. However, in some cases x-ray diffraction cannot unambiguously determine the correct atomic structure, which hampers further research. In this paper, we analyze the atomic ordering using spectroscopic ellipsometry-a simple tabletop method that researchers can use in situ during sample deposition. The Co2Fe(Ga0.5Ge0.5) Heusler compound was chosen for the analysis, as the atomic ordering greatly influences its spin-polarizing capabilities. The ellispometric results are confronted with x-ray diffraction and with the help of ab initio calculations the qualitative changes in the optical response are linked to the changes in atomic ordering.

We present experimental XMLD spectra measured on epitaxial (001)-oriented thin Co_2FeSi films, which are rich in features and depend sensitively on the degree of atomic order and interdiffusion from capping layers. Al- and Cr-capped films with different degrees of atomic order were prepared by DC magnetron sputtering by varying the deposition temperatures. The local structural properties of the film samples were additionally investigated by nuclear magnetic resonance (NMR) measurements. The XMLD spectra of the different samples show clear and uniform trends at the L_3,2 edges. The Al-capped samples show similar behavior as previous measured XMLD spectra of Co_2FeSi_0.6Al_0.4. Thus, we assume that during deposition Al atoms are being implanted into the subsurface of Co_2FeSi. Such an interdiffusion is not observed for the corresponding Cr-capped films, which makes Cr the material of choice for capping Co_2FeSi films. We report stronger XMLD intensities at the L_3,2 Co and Fe egdes for films with a higher saturation magnetization. Additionally, we compare the spectra with ab initio predictions and obtain a reasonably good agreement. Furthermore, we were able to detect an XMCD signal at the Si L-edge, indicating the presence of a magnetic moment at the Si atoms.

The semiconducting half-Heusler compound YPtSb has been predicted to convert into a topological insulator under the application of an appropriate degree of strain. In this study, p-type semiconducting YPtSb thin films were prepared by magnetron co-sputtering, using a specially designed target. YPtSb thin films grown on MgO (100) substrates at 600 degrees C showed a textured structure with the (111) plane parallel to the (001) plane of MgO. Electrical measurements showed that the resistivity of the YPtSb films decreases with increasing temperature, indicating semiconductor-like behavior. The carrier density was as high as 1.15 x 10(21) cm(-3) at 300 K. The band gap of the YPtSb thin films was around 0.1-0.15 eV, which was in good agreement with the theoretical prediction and the value measured for bulk YPtSb. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Pulsed laser deposition was employed to grow thin films of the Heusler compounds Co2MnSi and Co2FeSi. Epitaxial growth was realized both directly on MgO(1 0 0) and on a Cr or Fe buffer layer. Structural analysis by x-ray and electron diffraction shows for both materials the ordered L2(1) structure. Bulk magnetization was determined with a SQUID magnetometer. The values agree with the Slater-Pauling rule for half-metallic Heusler compounds. On the films grown directly on the substrate measurements of the Hall effect have been performed. The normal Hall effect is nearly temperature independent and points towards a compensated Fermi surface. The anomalous contribution is found to be dominated by skew scattering. A remarkable sign change in both normal and anomalous Hall coefficients is observed on changing the valence electron count from 29 (Mn) to 30 (Fe).