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DS: Fachverband Dünne Schichten

DS 4: Thin Film Characterisation II: Structure Analysis and Composition

DS 4.3: Vortrag

Montag, 16. März 2015, 15:30–15:45, H 0111

Twisted twin domains in epitaxial thin MnSi layers on Si(111) — •Mirko Trabel, Benedikt Halbig, Nadezda V. Tarakina, Christoph Pohl, Utz Bass, Charles Gould, Jean Geurts, Karl Brunner, and Laurens W. Molenkamp — Experimentelle Physik 3, Physikalisches Institut, Universität Würzburg, Am Hubland, D-97074, Würzburg, Germany

Thin layers of MnSi are grown by molecular beam epitaxy on Si(111) substrates and their crystal properties are investigated by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) measurements. Both XRD analysis and the observed Raman phonon modes prove that the layers of 5 - 32 nm thickness are single phase MnSi. The B20 crystal structure of MnSi lacks inversion symmetry and allows right- and left-handed crystals. We demonstrate by azimuthal φ -scans of several asymmetric X-ray reflections that certain reflections reveal the formation of twin domains in the layer as well as their corresponding azimuthal twists of Δφ=± 30^∘ with respect to the Si substrate. The observed intensities of corresponding reflexes are equal, indicating the same volume fractions for both domains. Cross-sectional TEM confirms the formation of the twisted twin domains and reveals a typical domain size of about 200 nm. The sheet resistivity shows the same temperature dependence as bulk MnSi with helical magnetic order, but the critical temperature is increased from the bulk value of 29.5 K to about 40 - 45 K.