Thin films of new materials with high spin polarization
Final Report Abstract
This project was focused on the preparation and investigation of thin film Heusler samples. These materials had been marked as potential half-metals. At the first stage, thin film deposition needed to be optimized in order to create epitaxial samples with minimal atomic disorder. Sample quality was analyzed with X-ray and electron diffraction as well as with magnetometry. Surface morphology was investigated with scanning electron and atomic force microscopy. First results obtained with sputter deposited samples showed a clear correlation between disorder and degraded magnetic properties. In order to improve sample quality, an ultra-high vacuum system for pulsed laser deposition was set up in the course of this project. The films fabricated with this technique show small disorder, the magnetic moments are compatible with the Slater-Pauling rule for half-metallic Heusler compound. A very smooth surface is advantageous for tunneling experiments or Brillouin light scattering spectroscopy. Additionally, the laser deposition system allowed the systematic variation of the sample stoichiometry. Especially the transport properties of quarternary samples with the stoichiometry Co2(Mn,Fe)Si were investigated and the data compared with theoretical results from Project 1. The normal Hall effect shows a systematic variation with changing Fe / Mn ratio in the samples. This evolution could be correlated with a change of the calculated Fermi surface topology. The anomalous Hall-effect shows a corresponding behaviour. In this case the signal is caused by opposing external and intrinsic mechanisms. Furthermore, the thin film samples prepared in this project were handed to Projects 5, 9 and 10 for additional investigations. Especially an inversion of XMCD spectra confirms the observations made by transport experiments. The use of a vacuum transport chamber allowed the application of surface sensitive techniques.
Publications
- (2006): Epitaxial film growth and magnetic properties of Co2FeSi. In: Phys. Rev. B 74 (17), S. 174426
H. Schneider, G. Jakob, M. Kallmayer, H. J. Elmers, M. Cinchetti, B. Balke, S. Wurmehl, C. Felser, M. Aeschlimann, and H. Adrian
(See online at https://doi.org/10.1103/PhysRevB.74.174426) - (2009): Hall effect in laser ablated Co 2 (Mn,Fe)Si thin films. In: J. Phys. D: Appl. Phys. 42 (8), S. 84012
H. Schneider, E. Vilanova Vidal, B. Balke, C. Felser, and G. Jakob
(See online at https://doi.org/10.1088/0022-3727/42/8/084012) - (2010): Hall effect and electronic structure of films. In: Journal of Magnetism and Magnetic Materials 322 (6), S. 579–584
H. Schneider, E. Vilanova Vidal, S. Chadov, G. H. Fecher, C. Felser, G. Jakob
(See online at https://doi.org/10.1016/j.jmmm.2009.09.048)
