Stabilization of magnetic helix in exchange-coupled thin films

Abstract

Based on micromagnetic simulations, we report on a novel magnetic helix in a soft magnetic film that is sandwiched between and exchange-coupled to two hard magnetic layers with different anisotropies. We show that such a confined helix stays stable without the presence of an external magnetic field. The magnetic stability is determined by the energy minimization and is a result of an internal magnetic field created by the exchange interaction. We show that this internal field stores a magnetic energy density of a few kJ/m3. We also find that it dramatically modifies ferromagnetic resonances, such that the helix can be used as a ferromagnetic resonance filter and a fast acting attenuator.

Topologically stable helices in exchange coupled rare-earth/rare-earth multilayer with superspin-glass like ordering

“…Thus, the appearance of H EB and the onset of spin blocking/freezing (T F (0)) may not be interdependent. The physical origin of exchange-coupling is rather due to the two hard magnetic layers with two different anisotropies 5 .…”

“…With removal of the external field, the multilayer typically relaxes into a ground state as all magnetic moments remain aligned and attains a global minimum. However, for an intermediate field, the stack relaxes into a metastable state as the spins remain misoriented with the attainment of a number of local energy minima 5,8 . In the present context, Fig.…”

“…The quantized energy spectrum within finite magnetic chains results in stabilizing topologically protected configurations of helices. Such helices, initially twisted in an external magnetic field, stay stable even without the presence of a field as they are created by exchange interaction and does not allow a trivial unwinding 5 .…”

Realizing topological stability of magnetic helices in exchange-coupled multilayers for all-spin-based system

“…Based upon micromagnetic simulations, Dzemiantsova et al . reported on magnetic helices in a soft magnetic film sandwiched between two hard magnetic layers with different anisotropies 5 . Very recently, Paul et al ., have shown the stability of vortex-like structures in Er-Tb multilayers 3 .…”

“…and Dzemiantsova et al . have shown the usages and possibility of nano-sized stable helices for magnetic energy storage 2 5 . In another example, the magnetization process of a two-dimensional random anisotropy system was shown numerically to be directly connected with topologically stable 2 π DWs, with vortices at each end 6 .…”