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- ItemTuning functional properties by plastic deformation(Milton Park : Taylor & Francis, 2009) Kwon, A.R.; Neu, V.; Matias, V.; Hänisch, J.; Hühne, R.; Freudenberger, J.; Holzapfel, B.; Schultz, L.; Fähler, S.It is well known that a variation of lattice constants can strongly influence the functional properties of materials. Lattice constants can be influenced by external forces; however, most experiments are limited to hydrostatic pressure or biaxial stress. Here, we present an experimental approach that imposes a large uniaxial strain on epitaxially grown films in order to tune their functional properties. A substrate made of a ductile metal alloy covered with a biaxially oriented MgO layer is used as a template for growth of epitaxial films. By applying an external plastic strain, we break the symmetry within the substrate plane compared to the as-deposited state. The consequences of 2% plastic strain are examined for an epitaxial hard magnetic Nd2Fe14B film and are found to result in an elliptical distortion of the in-plane anisotropy below the spin-reorientation temperature. Our approach is a versatile method to study the influence of large plastic strain on various materials, as the MgO(001) layer used is a common substrate for epitaxial growth.
- ItemDomain evolution during the spin-reorientation transition in epitaxial NdCo5 thin films(Milton Park : Taylor & Francis, 2013) Seifert, M.; Schultz, L.; Schäfer, R.; Neu, V.; Hankemeier, S.; Rössler, S.; Frömter, R.; Oepen, H.P.The domain structure and its changes with temperature were investigated for an epitaxial NdCo5 thin film with in-plane texture in which a spin-reorientation transition takes place from the easy c-axis via the easy cone to the easy plane. Scanning electron microscopy with polarization analysis reveals a transition from a two-domain state at temperatures above 318 K via a four-domain state back to a 90°-rotated two-domain state at temperatures below 252 K. The transition temperatures correspond well to those determined by global magnetization measurements. The magnetization configuration at the three different regimes of magnetic anisotropy and its transition with temperature were analysed in detail. From the local measurements, the spin-reorientation angle and the magnetocrystalline anisotropy constants of first and second order were derived.