TY - JOUR AB - 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. AU - Wortmann, Martin AU - Samanta, Tapas AU - Gaerner, Maik AU - Westphal, Michael AU - Fiedler, Johannes AU - Ennen, Inga AU - Hütten, Andreas AU - Blachowicz, Tomasz AU - Caron, Luana AU - Ehrmann, Andrea ID - 4178 IS - 12 JF - APL Materials KW - Magnetic ordering KW - Crystallographic defects KW - Electron diffraction KW - Epitaxy KW - Ferromagnetic materials KW - Magnetic hysteresis KW - Magnetic materials KW - Thin films KW - Transmission electron microscopy KW - Solid solid interfaces TI - Isotropic exchange-bias in twinned epitaxial Co/Co3O4 bilayer VL - 11 ER - TY - JOUR AB - 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. AU - Fokin, Nadine AU - Grothe, Timo AU - Mamun, Al AU - Trabelsi, Marah AU - Klöcker, Michaela AU - Sabantina, Lilia AU - Döpke, Christoph AU - Blachowicz, Tomasz AU - Hütten, Andreas AU - Ehrmann, Andrea ID - 654 IS - 7 JF - Materials KW - ferrimagnetic materials KW - superparamagnetism KW - magnetic hysteresis KW - magnetic materials KW - magnetic nanoparticles KW - nanocomposites KW - nanowires SN - 1996-1944 TI - Magnetic Properties of Electrospun Magnetic Nanofiber Mats after Stabilization and Carbonization VL - 13 ER -