| AVS 64th International Symposium & Exhibition | |
| Applied Surface Science Division | Thursday Sessions |
| Session AS+SS-ThA |
| Session: | Advances in Instrumentation and Data Analysis |
| Presenter: | Gary Mankey, University of Alabama |
| Authors: | B.D. Clark, University of Alabama N. Naghibolashrafi, University of Alabama S. Gupta, University of Alabama J. Jones, University of Alabama P.R. LeClair, University of Alabama A. Gupta, University of Alabama G.J. Mankey, University of Alabama |
| Correspondent: | Click to Email |
Half metallic alloys have a wide range of applications such as spin filters, spin polarizers, and high signal giant magnetoresistive devices. The Heusler family of alloys is predicted to have a large number of half-metallic alloys. The MINT Center at UA maintains an extensive database of Heusler alloys (http://heusleralloys.mint.ua.edu/) to track and contribute to the application of Heuslers in technology applications. The formation of stable crystal structures that match theoretical predictions is one issue that we are addressing experimentally. In this work, high temperature magnetron sputtering is applied in an attempt to stabilize predicted phases. The sputtering system is confocal with four targets, so alloy composition can be controlled by carefully adjusting the power to separate magnetron guns containing elemental targets of Fe, Mn, and Ge. Both in-situ and ex-situ techniques are applied to evaluate the resulting films. For in-situ flux monitoring, a quartz crystal microbalance is used; for in-situ chemical analysis, Auger electron spectroscopy with a cylindrical mirror analyzer is performed; and for in-situ structural analysis, reflection high-energy electron diffraction is performed. The ex-situ techniques employed include x-ray reflectivity and diffraction, scanning transmission microscopy with selected area diffraction, energy dispersive x-ray analysis, and variable temperature magnetometry and transport. Our characterization results show that when deposited on sapphire, the full-Heusler Fe2MnGe forms in the hexagonal DO19 crystal structure instead of the predicted L21 phase. The equiatomic half-Heusler alloy of FeMnGe forms in the C1b crystal structure when deposited on MgO(100). The results underline the importance of complete complimentary characterization techniques that include both chemical and structural analysis since the principle x-ray diffraction peaks of the L21 and C1b structures occur at the same locations. The two types of alloy films that were fabricated also exhibit markedly different magnetic behavior which will be discussed in detail.
We acknowledge MINT support through shared facilities. The work was supported by NSF DMREF Grant No. 1235396.