Vortex state in magnetic rings (original) (raw)
Related papers
Metastable states during magnetization reversal in square permalloy rings
Physical Review B, 2003
The magnetic reversal process in a two-dimensional array of permalloy square rings is presented. Rings of thickness of 25 nm, of lateral size of 2.1 m, and with ring width of 240 nm were microfabricated using electron-beam lithography and lift-off techniques. Analysis of the diffracted magneto-optical Kerr effect hysteresis loops, magnetic force microscopy images, and micromagnetic simulations show that the magnetization reversal path depends on the direction of the in-plane applied magnetic field. On reducing the field from saturation, for fields along an edge or a diagonal of the square, the ''onion'' state is the stable state at remanence. In a narrow field range around reversal we find that the reversal occurs via a metastable intermediate state. For fields along the diagonal this intermediate state is a magnetic vortex. When the field is applied along an edge direction the intermediate state is a ''horseshoe'' state.
Abstract: The Magnetic ProPerties of subMicron ferroMagnetic rings have attracted considerable attention since they show unique ProPerties that May hold great Potential for technological aPPlications such as highYdensity storage or Magnetic randoM access MeMory (MRaM). Recent studies on Co and PerMalloy rings have shown that a totally fluxYclosed Magnetic vortex structure is stable at reManence. The two chiralities of the vortex, clockYwise and antiYclockYwise, have been ProPosed as the carriers for the ...
Control of magnetic vortex chirality in square ring micromagnets
Journal of Applied Physics, 2005
We investigate the effect of a deliberately introduced shape asymmetry on magnetization reversal in small, square-shaped, magnetic rings. The magnetization reversal process is investigated using the diffracted magneto-optical Kerr effect combined with micromagnetic simulations. Experimentally we find that the reversal path is sensitive to small ͑±1°͒ changes in the direction of the applied field. Micromagnetic simulations that reproduce the measured zeroth-and first-order loops allow us to identify the reversal mechanisms as due to different intermediate states, namely, the so-called vortex and horseshoe states. Based on our results we are now able to prescribe a methodology for writing a vortex state with specific chirality in these asymmetric rings. Such control will be necessary if patterned arrays of this kind are to be used as magnetic storage elements.
Domain-specific magnetization reversals on a Permalloy square ring array
Journal of Applied Physics, 2004
We present domain-specific magnetization reversals extracted from soft x-ray resonant magnetic scattering measurement on a permalloy square ring array. The extracted domain-specific hysteresis loops reveal that the magnetization of the domain parallel to the field is strongly pinned, while those of other domains rotate continuously. In comparison with the micromagnetic simulation, the hysteresis loop on the pinned domain indicates a possibility of the coexistence of the square rings with the vortex and onion states.
Magnetization reversal in arrays of Co rings
2003
The magnetic properties of ferromagnetic rings have attracted considerable attention since they show unique properties that may hold great potential for technological applications such as high-density storage or magnetic random access memory MRAM. 1 Recent studies2–4 of Co rings with various sizes have shown that a totally flux-closed magnetic vortex structure is stable at remanence.
Magnetization reversal of thin Fe triangular rings
Superlattices and Microstructures, 2007
We have investigated the magnetization reversal of two regular arrays of Fe triangular microwire rings (base 7.3 µm and 2.8 µm, periodicity 11.5 µm and 5.6 µm, respectively) using the magneto-optical Kerr effect in vector-MOKE and Bragg-MOKE configuration. The measurements are compared with the results of micromagnetic simulations, which allow a detailed interpretation of the experimental data. We find that the magnetization reversal in an external magnetic field depends on the size of the triangles. Domain formation is more pronounced in the large than in the small triangular rings, and micromagnetic simulations show a vortex state in the small triangular rings.
We manipulate the magnetic states of ferromagnetic nanorings with an azimuthal Oersted field directed along the ring circumference. The circular field is generated by passing current through an atomic force microscope tip positioned at the center of the ring, and can directly control the chirality of the vortex state. We demonstrate switching from an onion state to a vortex state and between two vortex states, using magnetic force microscopy to image the resulting magnetic states. The understanding of the magnetization switching behavior in an azimuthal Oersted field could improve practical magnetic data storage devices.
Flux-Closure Magnetic States in Triangular Cobalt Ring Elements
IEEE Transactions on Magnetics, 2000
Ferromagnetic ring elements on the micrometer and submicrometer scale exhibit flux-closure magnetic vortex states in an intermediate step of their magnetization reversal. These clockwise or counterclockwise flux-closure states are of interest for applications that encode binary information in magnetic elements. Here, we study the magnetization reversal process of triangular cobalt rings made by e-beam lithography and lift-off. We demonstrate that full control over the direction of flux-closure magnetic states can be achieved solely by homogeneous external magnetic fields applied in particular directions. We have extracted statistical experimental data pertaining to the range of critical field values that trigger magnetization reversal from magnetic force microscopy images, and we explain the results on the basis of micromagnetic simulations.
Magnetization reversal in patterned double-vortex structures
Journal of Applied Physics, 2005
The magnetization reversal process for micron and submicron disk-shaped dots is controlled by successive nucleation, displacement, and annihilation of a magnetic vortex. Here the reversal process for a system involving two ferromagnetic disks separated by a nonmagnetic spacer is investigated experimentally, analytically, and numerically. Permalloy ͑Ni 80 Fe 20 or Py͒ dots with thicknesses of up to 40 nm and diameters of 0.5-2.5 m separated by a copper spacer ͑1-45 nm thick͒ were considered. Micromagnetic simulations indicate that the disks will each support oppositely directed vortices at remanence and also show the hysteresis of the coupled structures. The calculations are compared to hysteresis loops and x-ray photoemission electron microscopy images of Py/ Cu/ Py dots produced by electron-beam lithography and magnetron sputtering.