Regensburg 2010 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
MA: Fachverband Magnetismus
MA 8: Magnetic Shape Memory Alloys
MA 8.7: Vortrag
Montag, 22. März 2010, 16:45–17:00, H22
Free-standing epitaxial Ni2MnGa films — •Tobias Eichhorn, Peter Klaer, Hans-Joachim Elmers, and Gerhard Jakob — Institut für Physik, Universität Mainz, Deutschland
Among the compounds crystallizing in the Heusler structure many systems are of interest due to their predicted high spin polarization making them potential materials for spintronic devices. On the contrary Ni2MnGa is attracting high scientific interest by presenting a ferromagnetic shape memory effect in the low temperature phase (martensite). Moderate magnetic fields can induce large reversible length changes up to 10 % in martensitic single crystals. Thereby actuators and sensors with a compact design can be realised using single crystalline thin films of the material. The investigated films are prepared on heated Al2O3(11-20) and MgO(100) substrates by dc-magnetron sputtering from alloy targets of different stoichiometry. Samples deposited from a Mn-rich target are martensitic at room temperature and show a modulated orthorhombic structure (7M). The complex crystal structure is studied by x-ray diffraction in 4-circle geometry. Magnetic properties are investigated by magnetometry, x-ray absorption spectroscopy and magnetic circular dichroism measurements. Since rigid substrates block magnetically induced strains free-standing films will be needed. One route is to deposit on NaCl(100) substrates that can be easily dissolved in water. The released films are strongly textured, but not single crystalline as desired. Improved crystal quality can be reached by another approach, i.e. introducing a buffer layer on MgO(100) that can be etched selectively. This work is part of SPP 1239.