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 15.153: Poster
Dienstag, 27. März 2007, 15:00–19:00, Poster A
Characterization of Magnetic Structure in NiMnGa Alloys by Means of Lorentz Electron Microscopy and Electron Holography — •Karin Vogel1, Dorin Geiger1, Hannes Lichte1, Werner Skrotzki1, Robert Chulist1, Uwe Gaitzsch2, Martin Pötschke2, Stefan Roth2, and Andrea Böhm3 — 1Institute for Structure Physics, TU Dresden, 01062 Dresden — 2IFW Dresden, P.O. Box 270116, 01171 Dresden — 3Fraunhofer IWU, 01187 Dresden
The magnetic field induced strain (MFIS) in NiMnGa alloys is based on easy motion of twin boundaries. Therefore, it is necessary to understand the influence of microstructural parameters on twin boundary motion. We investigate microstructure and magnetic structure of martensitic NiMnGa alloys by conventional transmission electron microscopy (TEM) and Lorentz TEM, as well as electron holography (EH). TEM offers characterization of nano-features like twin boundaries, grain boundaries, precipitates, etc.; Lorentz TEM allows analysing the coarse magnetic structure, e.g. magnetic domain boundaries; EH is used to determine the fine-scale distribution of magnetization, e.g. inside the domains. We use a Philips CM200 TEM equipped with a Lorentz lens and an electron biprism. The conventional in-focus TEM images show the twin-band structure of the martensitic material. From the Lorentz images, the correlation of magnetic domains with the twin band structure both in domain size and orientation follows. In the EH phase images, lines of equal phase display the 3D magnetization distribution projected into the recording plane. Financial support from DFG-SPP 1239 is gratefully acknowledged.