Magnetic Domain Propagation Research Articles

Magnetic domain propagation in Pt/Co/Pt micro wires with engineered coercivity gradients along and across the wire

Pt(15nm)/[Co(0.6nm)/Pt(1.5nm)]4 multilayers with perpendicular magnetic anisotropy were patterned into several-micrometer wide wires by electron-beam lithography. Bombarding the wires with He+ ions with a fluence gradient along the wire results in a spatial gradient of switching fields that allows a controllable positioning of domain walls. The influence of the reduced anisotropy near the wire edges causes a remanent state in which the reversal close to the long edges precedes that in the middle of the wires. Experiments using Kerr microscopy prove this effect and micromagnetic simulations corroborate that a decrease of the anisotropy at the edges is responsible for the effect.

Reversible strain control of magnetic anisotropy in magnetoelectric heterostructures at room temperature.

The ability to tune both magnetic and electric properties in magnetoelectric (ME) composite heterostructures is crucial for multiple transduction applications including energy harvesting or magnetic field sensing, or other transduction devices. While large ME coupling achieved through interfacial strain-induced rotation of magnetic anisotropy in magnetostrictive/piezoelectric multiferroic heterostructures has been demonstrated, there are presently certain restrictions for achieving a full control of magnetism in an extensive operational dynamic range, limiting practical realization of this effect. Here, we demonstrate the possibility of generating substantial reversible anisotropy changes through induced interfacial strains driven by applied electric fields in magnetostrictive thin films deposited on (0 1 1)-oriented domain-engineered ternary relaxor ferroelectric single crystals with extended temperature and voltage ranges as compared to binary relaxors. We show, through a combination of angular magnetization and magneto-optical domain imaging measurements, that a 90° in-plane rotation of the magnetic anisotropy and propagation of magnetic domains with low applied electric fields under zero electric field bias are realized. To our knowledge, the present value attained for converse magnetoelectric coupling coefficient is the highest achieved in the linear piezoelectric regime and expected to be stable for a wide temperature range, thus representing a step towards practical ME transduction devices.

Magnetoelastic Contribution in Domain Wall Propagation of Micrometric Wires

We report on studies of domain wall propagation of magnetically-bistable Fe-Co-rich microwires paying attention on the effect of applied and internal stresses. We measured magnetic domain propagation in various magnetic Fe-Co-rich amorphous microwires with metallic nucleus diameters (from 2.8 microm to 18 microm) using Sixtus Tonks-like experiments. We found that application of applied stresses and increasing of internal stresses result in decreasing of domain wall (DW) velocity. We assume that in order to achieve higher DW propagation velocity at the same magnetic field and enhanced DW mobility, special attention should be paid to the decrease of magnetoelastic energy.

Magnetization reversal in patterned La0.67Sr0.33MnO3 thin films by magneto-optical Kerr imaging

The magnetization reversal process in patterned La0.67Sr0.33MnO3 thin films has been studied at room temperature using the magneto-optical Kerr effect. The 100 and 200nm thick films were patterned into 50μm long rectangles of various widths in the 20–50μm range. In each rectangle, holes with 2 and 5μm diameters were patterned aiming at pinning the domain walls. X-ray diffraction study revealed high structural quality of both films. However, the macroscopic surface properties of both films were different, as shown by optical microscopy, which revealed cracks in the thicker film. For each thickness, both the magnetic domain images and the local magnetic hysteresis loops were recorded. For both films, the magnetization reversal process consists in nucleation and propagation of magnetic domains. In the 100nm thick film, the local hysteresis loops depend on the widths of the patterned rectangles and we observed a significant effect of the hole in pinning domains walls, leading to multiple switching transitions in the hysteresis loops. No such effect was observed inside the 200nm thick film containing cracks.

Lorentz microscopy of circular ferromagnetic permalloy nanodisks

Circular permalloy elements were fabricated by a combination of electron beam lithography, thermal evaporation and liftoff technique on electron transparent membrane substrates. The magnetic properties have been studied by Lorentz transmission electron microscopy. In situ magnetizing experiments have been carried out to obtain information about the nucleation and propagation of magnetic domains within the permalloy nanodisks and to determine the nucleation and saturation fields. The diameter of the patterned elements has been varied between 180 and 950 nm, the height was 15 nm. The experiments showed that the vortex configuration is the most favorable state in zero field conditions of all investigated permalloy nanodisks.