2017, Hilse, Maria, Jenichen, Bernd, Herfort, Jens

On the basis of semiconductor-ferromagnet GaAs-Fe3Si core-shell nanowires (Nws) we compare the facilities of magnetic Nw ensemble measurements by superconducting quantum interference device magnetometry versus investigations on single Nws by magnetic force microscopy and computational micromagnetic modeling. Where a careful analysis of ensemble measurements backed up by transmission electron microscopy gave no insights on the properties of the Nw shells, single Nw investigation turned out to be absolutely essential.

2005, Herfort, Jens, Ploog, Klaus H.

[no abstract available]

2000, Däweritz, Lutz, Hey, Rudolf, Herfort, Jens

[no abstract available]

2015, Tominaga, Junji, Kolobov, Alexander V., Fons, Paul J., Wang, Xiaomin, Saito, Yuta, Nakano, Takashi, Hase, Muneaki, Murakami, Shuichi, Herfort, Jens, Takagaki, Yukihiko

Multiferroics, materials in which both magnetic and electric fields can induce each other, resulting in a magnetoelectric response, have been attracting increasing attention, although the induced magnetic susceptibility and dielectric constant are usually small and have typically been reported for low temperatures. The magnetoelectric response usually depends on d-electrons of transition metals. Here we report that in [(GeTe)2(Sb2Te3)l]m superlattice films (where l and m are integers) with topological phase transition, strong magnetoelectric response may be induced at temperatures above room temperature when the external fields are applied normal to the film surface. By ab initio computer simulations, it is revealed that the multiferroic properties are induced due to the breaking of spatial inversion symmetry when the p-electrons of Ge atoms change their bonding geometry from octahedral to tetrahedral. Finally, we demonstrate the existence in such structures of spin memory, which paves the way for a future hybrid device combining nonvolatile phase-change memory and magnetic spin memory.

2005, Ploog, Klaus H., Herfort, Jens, Ramsteiner, Manfred, Trampert, Achim, Friedland, Klaus-Jürgen

[no abstract available]

2021, Terker, Markus, Nicolai, Lars, Gaucher, Samuel, Herfort, Jens, Trampert, Achim

Isothermal crystallization of amorphous Ge deposited on a cubic Fe3Si/GaAs(001) substrate is performed by in situ annealing within a transmission electron microscope. It was found that the formation of epitaxially aligned tetragonal FeGe2 is associated with a disorder–order phase transition mainly consisting of a rearrangement of the Fe/vacancy sublattice from a random distribution to alternating filled and empty layers. Additionally, atomically resolved high-angle annular dark-field scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy demonstrated that the vertical lattice spacing of the Ge sublattice reduces across vacancy layers, indicating that strain minimization plays a role in the phase transition process. Crystallization and ordering are both found to proceed layer-by-layer and with square-root-shaped kinetics with a smaller transition rate for the latter.

2009, Herfort, Jens, Koch, Reinhold, Trampert, Achim

[no abstract available]