Tailoring magnetic vortices in nanostructures

Abstract

Tailoring the properties of magnetic vortices through the preparation of structured multilayers is discussed. The dependence of the vortex core radius r on the effective anisotropy is derived within a simple model, which agrees with our simulations. As the perpendicular anisotropy increases, r also increases until a perpendicular magnetization appears in the disk rim. Co/Pt multilayer disks were studied; x-ray microscopy confirms qualitatively the predicted behavior. This is a favorable system for implementing vortex-based spin-transfer nano-oscillator devices, with enhanced rf power resulting both from the increase in the core size and synchronization afforded by the coupling of the Co layers.

Properties of magnetic nanodots with perpendicular anisotropy

“…Using the magnetic parameters 25 for bulk Co, (the exchange length is l ex = 4.93 nm), we obtain the core size in the presence of perpendicular anisotropy, as shown in Fig. 4, in good agreement with Fig.…”

“…For higher anisotropies another more complex configuration appears with an out-of-plane magnetization at the disk rim (region d), as observed experimentally in ref. 25 . Increasing the perpendicular anisotropy increases the vortex core radius, and eventually leads to a more complex spin structure, with the magnetization at the disk rim pointing down (Fig.…”

“…We have recently shown theoretically and experimentally 25 , that using Co/Pt multilayers it is possible to tailor the vortex core diameter by playing with the perpendicular anisotropy originated at the Co-Pt interface. When one increases the perpendicular anisotropy acting on a magnetic nanodot, e.g., reducing the Co layer thickness, the vortex core diameter increases, and eventually another vortex state appears, which is characterized by an out-of-plane magnetization component at the dot rim.…”

X-ray imaging of vortex cores in confined magnetic structures

“…In addition, it is found that the calculated core profile is narrower than in the experiments. In a second step, we included perpendicular anisotropy of K = 10 kJ/m 3 (corresponding to a moderate anisotropy field µ 0 H K = 250 G) [30] and we observed that the dip in the calculation becomes more pronounced with increasing sample thickness. The existence of a perpendicular anisotropy in NiFe films has been proposed in order to interpret the appearance of so-called weak stripes at large thickness [31].…”

Intrinsic nonadiabatic topological torque in magnetic skyrmions and vortices

“…Since the topological torque is an intrinsic property of the magnetic texture, one could continuously deform this structure by applying, e.g., a perpendicular external magnetic field [62,63] and therefore influence the nonadiabaticity parameter. For instance, Moreau-Luchaire et al [32] demonstrated a reduction of the skyrmion diameter from 80 nm at 12 mT to 30 nm at 70 mT.…”