Domain configuration of permalloy ellipses in a rotating magnetic field

Abstract

The domain configuration of micron-sized permalloy ellipses was studied under the influence of an in-plane rotating magnetic field using magnetic force microscopy. The field amplitude was chosen such that when the field is applied parallel to the long axis of the ellipses they are saturated, but when the field is perpendicular to the long axis they exhibit multi-domain states. The rotation angle for nucleation and annihilation of domains was determined for different magnitudes of the applied magnetic field and for two different lateral sizes of ellipses, 6 µm × 2 µm and 3 µm × 1 µm. It was found that both nucleation and annihilation occur over a range of angles for both lateral sizes of ellipses. Saturated states are stable for a wider range of angles for larger values of the applied field.

Micromagnet arrays enable precise manipulation of individual biological analyte–superparamagnetic bead complexes for separation and sensing

“…40 The in-plane rotating magnetic field determined the distortion, annihilation and nucleation of the magnetic domains inside the ellipses. 41 The beads followed the net 98 (b) In ring structures, two magnetic domains are formed that are separated by a HH and a TT domain walls ("onion-like" state). The in-plane rotation of the magnetic field shifts the domain walls along the perimeter of the conduit, thus transporting the SPM beads (grey spheres).…”

“…38,39 Standard lithographic patterning techniques have been used to create micromagnet arrays with 1 to 10 μm scale dimensions. [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59] These SFEs are easily de-magnetised in the presence of 5 to 15 kA m −1 in-plane magnetic fields (H xy ). Bead transport has been studied on a number of SFE designs, i.e., ellipses, [40][41][42]44,51 connected disks or half-disks, 46,53,56,57 disks, [47][48][49][50]52,54,55,59 triangles, 45,55 and more complex configurations, 43,58 using external magnetic fields created by electromagnets or by the rotation of permanent magnets.…”

Simulations of magnetic microstructure in thin film elements used for programmable motion of magnetic particles

“…The angle for the nucleation of a multi-domain state is similar to the angle observed for the smaller element. It should be noticed that the multi-domain state remains for larger rotation angles until it is finally annihilated for a certain rotation angle [7]. …”

Magnetic properties of elliptical and stadium-shaped nanoparticles: Effect of the shape anisotropy

“…Also Alexeev et al [7] studied the magnetization configurations in elliptical Fe 0.7 Cr 0.3 particles with sizes of 0:6 Â 0:3 Â 0:015 mm 3 . Besides, the reversal processes of nanosized elliptical permalloy magnetic dots with various aspect ratios have been investigated [8][9][10][11][12][13][14][15]. For example, Lee et al [9] have found the following states for magnetization reversal in elliptical particles: single vortex, double vortex and vortex-free reversal.…”

“…Buchanan et al [12] reported the magnetic field tunability of the translational mode that corresponds to spiral-like precession of the vortex core around its equilibrium position in permalloy ellipses. Felton et al [13] investigated the domain configuration of micron-sized permalloy ellipses under the influence of an in-plane rotating magnetic field. Finally, spin-waves (SW) modes excited in a submicron permalloy ellipse with a vortex pair configuration have been addressed by Zhang et al [15].…”