Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)

MA 15.155: Poster

Dienstag, 27. März 2007, 15:00–19:00, Poster A

MBE-thin film growth of NiMn-based magnetic shape memory alloys — •Ralf Hassdorf^1,3, Jürgen Feydt², and Michael Moske¹ — ¹Thin adaptive films, Research center caesar, 53175 Bonn — ²Electron microscopy, Research center caesar — ³Institute of Condensed Matter Physics, TU Braunschweig, 38106 Braunschweig

In a previous study, we reported on (111) highly oriented Ni-Mn-Al grown films, deposited on amorphous thermal SiO₂. TEM images revealed the occurrence of modulated martensitic structures, more precisely a striped morphology of 2M and 14M within the single grains [1]. By varying the film composition the austenite/martensite transition boundary was experimentally obtained, in accordance with e/a-dependency predictions. In a theoretical approach, using ab initio calculations, we confirmed that in the system Ni-Mn-Al the cubic L2₁ Heusler structure is unstable against shear displacement along the [110] direction which promotes lattice modulation [2].

Here, we report on single-crystal films grown on several different single crystalline substrates with different orientations, i.e., on MgO (001), α-Al₂O₃ (0001) and (11-20) as well as on GaAs (001). For the latter, specifically, Ga is incorporated into the film structure almost homogeneously arising from a solid state reaction at the film-substrate interface. This opens up the possibility for exploring compositions with an isoelectronic substitution, here, Al vs Ga. The compositional and microstructural aspects will be discussed.

[1] R. Hassdorf et al., Mater. Res. Soc. Symp. Proc. 785, 57 (2004).

[2] T. Büsgen et al., Phys. Rev. B 70, 014111 (2004).