@article{4178, abstract = {Exchange bias (EB) is a unidirectional anisotropy caused by interface coupling between a ferromagnet and an antiferromagnet. It causes a preferential direction of magnetization in the ferromagnet, which manifests as a shift of the hysteresis loop along the magnetic field axis. Here, we demonstrate a large EB of over 1000 Oe at 20 K in a twinned Co(111)/Co3O4(111) thin film epitaxially grown on sapphire(0001) with sixfold rotational lattice symmetry, which is among the highest values reported for Co/Co1−yO systems. In such systems, the effect intensity is largest along the magnetic easy axes, which usually results in an anisotropy of the EB in epitaxial interfaces. However, we observed identical EB values for 0°, 15°, and 30° angles between the magnetic field and the nearest Co[002] magnetic easy axes. The measurements imply a relaxation of the magnetization to the nearest easy axis, suggesting increasingly isotropic EB fields with higher orders of rotational lattice symmetry. }, author = {Wortmann, Martin and Samanta, Tapas and Gaerner, Maik and Westphal, Michael and Fiedler, Johannes and Ennen, Inga and Hütten, Andreas and Blachowicz, Tomasz and Caron, Luana and Ehrmann, Andrea}, issn = {2166-532X}, journal = {APL Materials}, keywords = {Magnetic ordering, Crystallographic defects, Electron diffraction, Epitaxy, Ferromagnetic materials, Magnetic hysteresis, Magnetic materials, Thin films, Transmission electron microscopy, Solid solid interfaces}, number = {12}, publisher = {AIP Publishing}, title = {{Isotropic exchange-bias in twinned epitaxial Co/Co3O4 bilayer}}, doi = {10.1063/5.0183566}, volume = {11}, year = {2023}, } @article{654, abstract = {Magnetic nanofibers are of great interest in basic research, as well as for possible applications in spintronics and neuromorphic computing. Here we report on the preparation of magnetic nanofiber mats by electrospinning polyacrylonitrile (PAN)/nanoparticle solutions, creating a network of arbitrarily oriented nanofibers with a high aspect ratio. Since PAN is a typical precursor for carbon, the magnetic nanofiber mats were stabilized and carbonized after electrospinning. The magnetic properties of nanofiber mats containing magnetite or nickel ferrite nanoparticles were found to depend on the nanoparticle diameters and the potential after-treatment, as compared with raw nanofiber mats. Micromagnetic simulations underlined the different properties of both magnetic materials. Atomic force microscopy and scanning electron microscopy images revealed nearly unchanged morphologies after stabilization without mechanical fixation, which is in strong contrast to pure PAN nanofiber mats. While carbonization at 500 °C left the morphology unaltered, as compared with the stabilized samples, stronger connections between adjacent fibers were formed during carbonization at 800 °C, which may be supportive of magnetic data transmission.}, author = {Fokin, Nadine and Grothe, Timo and Mamun, Al and Trabelsi, Marah and Klöcker, Michaela and Sabantina, Lilia and Döpke, Christoph and Blachowicz, Tomasz and Hütten, Andreas and Ehrmann, Andrea}, issn = {1996-1944}, journal = {Materials}, keywords = {ferrimagnetic materials, superparamagnetism, magnetic hysteresis, magnetic materials, magnetic nanoparticles, nanocomposites, nanowires}, number = {7}, title = {{Magnetic Properties of Electrospun Magnetic Nanofiber Mats after Stabilization and Carbonization}}, doi = {10.3390/ma13071552}, volume = {13}, year = {2020}, }