@article{2284, abstract = {Improved magnetic memory systems belong to the main research topics in spintronics. Here we show micromagnetic simulations used to analyze the energy density of nano-scaled iron spheres. Layers of different thickness, partly coated with iron oxide, were tested in terms of spatial uniformity of the physical system energy. For a single non-coated or iron-oxide coated droplet, the spatial distribution of the total energy is not uniform and depends on the nano-droplet size. Additionally, for systems consisting of four objects, the relation between relative distance and the resultant magnetization distribution was analyzed. The mutual relation between droplet size and the underlying magnetization distribution as well as the character of local energy extrema was investigated. The size changes for the four-droplet system were compared with the single object behavior to obtain a criterion for the minimum distance between spheres to behave as a single object. The calculations revealed that the oxidized spheres could be placed closer to each other in comparison to the non-coated system. For the proposed oxide coated system, the increase of this maximum packing density is equal to about 12%, as compared to the non-coated system.}, author = {Steblinski, Pawel and Blachowicz, Tomasz and Ehrmann, Andrea}, issn = {03048853}, journal = {Journal of Magnetism and Magnetic Materials}, keywords = {Magnetic anisotropy, Ferromagnetism, Micromagnetism}, publisher = {Elsevier BV}, title = {{Analysis of the energy distribution of iron nano-spheres for bit-patterned media}}, doi = {10.1016/j.jmmm.2022.169805}, volume = {562}, year = {2022}, } @article{1580, abstract = {Magnetic nanofibers can be used for data transport and storage, especially related to the emerging field of neuromorphic computing. Domain walls in bent nanofibers can nucleate, e.g., due to rotating local magnetic fields. Their propagation through bent nanofibers, however, depends on the bending direction in correlation to the rotational orientation of the magnetic field, making such nanofibers suitable for semi-deterministic logic operations. Here we report on domain wall nucleation, propagation and annihilation in bent nanowire networks with multiple data inputs and outputs. Our results show the influence of the bending radii on domain wall nucleation and propagation, leading to suggestions for possible realization of multi-level systems for logic operations.}, author = {Blachowicz, T. and Steblinski, P. and Grzybowski, J. and Ehrmann, Andrea}, issn = {03048853}, journal = {Journal of Magnetism and Magnetic Materials}, keywords = {Nanofibers Magnetization dynamics Domain wall propagation Logic table Truth table}, publisher = {Elsevier BV}, title = {{Domain wall nucleation, propagation and annihilation in coupled bent ferromagnetic nanofibers with rotating local input fields}}, doi = {10.1016/j.jmmm.2021.168925}, volume = {546}, year = {2022}, } @article{1579, abstract = {Asymmetric hysteresis loops can be found in exchange-bias systems in which a ferromagnet is exchange-coupled with an antiferromagnet. In purely ferromagnetic samples, such effects can occur due to undetected minor loops or thermal effects. While the exchange bias is long established in hard-disk read/write heads and diverse spintronics applications, minor loops are sometimes used for the calculation of first order reversal curves (FORCs). Reports about their technological relevance, however, are scarce. Here we report on micromagnetic simulations of a nanoparticle with areas of varying height, consisting of tessellations of a defined area, in which the shape anisotropy in narrow higher lines opposes magnetization reversal stronger than in the larger, lower areas between, thus interacting similar to hard/soft magnetic materials although consisting of the same material and thus having identical magneto-crystalline anisotropy. After saturating this nanostructure by a strong magnetic field pulse, distinctly asymmetric, horizontally shifted hysteresis loops can be recognized, especially in the transverse magnetization component. We show the influence of the external magnetic field orientation on this asymmetry.}, author = {Ehrmann, Andrea and Blachowicz, T.}, issn = {03048853}, journal = {Journal of Magnetism and Magnetic Materials}, keywords = {Pseudo-exchange bias Micromagnetic simulation Hysteresis loops Magnetic nanostructure Tessellation}, publisher = {Elsevier BV}, title = {{Magnetization reversal asymmetry in a structured ferromagnetic nanoparticle with varying shape anisotropy}}, doi = {10.1016/j.jmmm.2021.168929}, volume = {546}, year = {2022}, } @article{1426, abstract = {Round magnetic nano-dots belong to the frequently investigated magnetic nanostructures since they can often reverse magnetization via a vortex state which is characterized by low stray fields, making them useful for data storage applications. Nano-rings, with an open aperture in the middle, regularly show flux-closed vortex states without a vortex core, again reducing stray fields. Here we theoretically investigate “Pac-Man” shaped iron nanostructures with varying aperture, i.e. structures ranging from a thin ring to a solid cylinder with a triangular cut. Our results show that in most cases, a vortex-like state without vortex core along the whole nanostructure occurs during magnetization reversal. Depending on the angle of the external magnetic field and the nanostructure thickness, different magnetization reversal processes have been found, including domain wall nucleation and propagation as well as small vortex states with cores. The occurrence of such special magnetic states can be attributed to the interaction of the shape anisotropy with the relatively high magneto-crystalline anisotropy of iron. Our simulations reveal the possibilities to use such structures for data storage applications as well as their importance in basic research, enabling formation of asymmetric magnetic structures beyond common onion and symmetric vortex states.}, author = {Bachar, Fatima-Zohra and Schröder, Christian and Ehrmann, Andrea}, issn = {03048853}, journal = {Journal of Magnetism and Magnetic Materials}, keywords = {Magnetic nanostructures Micromagnetic simulation Magnetization reversal Iron Vortex state Domain walls Shape anisotropy}, publisher = {Elsevier BV}, title = {{Magnetization reversal in Pac-Man shaped Fe nanostructures with varying aperture}}, doi = {10.1016/j.jmmm.2021.168205}, volume = {537}, year = {2021}, } @article{1616, abstract = {Electrospun nanofibers produced from magnetic materials form a magnetic network which may be used for neuromorphic computing and other novel applications. While the influence of bending radii on the magnetization reversal in such nanofibers was already discussed in the literature, the often occurring beads along the fibers have not yet been investigated in detail. It can be assumed that such beads will support domain wall formation due to a reduction of the relative impact of the shape anisotropy, in this way influencing magnetization reversal along the fiber. Here, we simulate magnetization reversal processes in iron, nickel, cobalt and magnetite fibers with a bead in the middle, produced in three typical dimensions gained by electrospinning. In most cases a vortex state occurs during magnetization reversal, independent from the material and the dimensions. For some angular orientations of the external magnetic field, double-vortex or meander states are visible, usually also followed by vortex states. These simulations underline the strong and highly reliable impact of beads along electrospun fibers, making these structures useful for data storage, transport and other applications.}, author = {Amini, Fedi and Blachowicz, Tomasz and Ehrmann, Andrea}, issn = {03048853}, journal = {Journal of Magnetism and Magnetic Materials}, keywords = {Magnetic nanostructures Micromagnetic simulation Magnetization reversal Iron Nickel Cobalt Magnetite Vortex state Domain walls Shape anisotropy}, publisher = {Elsevier BV}, title = {{Systematic study of magnetization reversal in beaded fibers from different magnetic materials}}, doi = {10.1016/j.jmmm.2021.167855}, volume = {529}, year = {2021}, } @article{2673, author = {Luciński, T and Urbaniak, M and Brückl, H and Hütten, A and Heitmann, Sonja and Reiss, G}, issn = {03048853}, journal = {Journal of Magnetism and Magnetic Materials}, pages = {1889--1891}, publisher = {Elsevier BV}, title = {{Magnetoresistance effect in asymmetric dual spin-valves—a device for three-state logic}}, doi = {10.1016/j.jmmm.2003.12.1249}, volume = {272-276}, year = {2004}, } @article{2674, author = {Luciński, T. and Hütten, A. and Brückl, H. and Heitmann, Sonja and Hempel, T. and Reiss, G.}, issn = {03048853}, journal = {Journal of Magnetism and Magnetic Materials}, number = {1}, pages = {78--88}, publisher = {Elsevier BV}, title = {{Magnetoresistance study of Ni80Fe20/Co1/CuAgAu/Co2 asymmetric sandwiches}}, doi = {10.1016/S0304-8853(03)00564-X}, volume = {269}, year = {2004}, } @article{1452, author = {Schröder, Christian and Schnack, J and Mentrup, D and Luban, M}, issn = {03048853}, journal = {Journal of Magnetism and Magnetic Materials}, pages = {E721--E723}, publisher = {Elsevier BV}, title = {{Critical slowing-down in classical and quantum Heisenberg magnetic molecules}}, doi = {10.1016/j.jmmm.2004.01.064}, volume = {272-276}, year = {2004}, } @article{2684, author = {Heitmann, Sonja and Hütten, A. and Hempel, T. and Schepper, W. and Reiss, G.}, issn = {03048853}, journal = {Journal of Magnetism and Magnetic Materials}, pages = {1752--1754}, publisher = {Elsevier BV}, title = {{Enhanced GMR amplitude and temperature stability of copper/permalloy combination multilayers}}, doi = {10.1016/S0304-8853(00)00885-4}, volume = {226-230}, year = {2001}, }