Spontaneous Asymmetry of Chiral Magnetic Domains Within a Magnetic Field

Abstract

Chiral magnetic domains are topological spin textures in which the Dzyaloshinskii–Moriya interaction assigns a given chirality to the domain walls. Notably, despite rapid progress in chiral magnetic research, one fundamental issue that remains unclear is how the chirality of chiral magnetic domains change as a magnetic field deforms the spin texture. Using spin‐polarized low energy electron microscopy, the evolution of Fe/Ni chiral magnetic stripe domains are investigated in single‐crystalline Fe/Ni/Cu/Co/Cu(001) multilayers in which the interlayer magnetic coupling between the Co and Fe/Ni films serves as an in‐plane magnetic field. Contrary to theoretical works, it is found that the chirality of the Néel walls results in a parallel alignment of the magnetic stripes with the in‐plane magnetic field direction. The transformation of chiral Néel walls into achiral Bloch walls can be precisely controlled by tuning the Cu spacer layer thickness. In addition, the domain wall exhibits a spontaneous asymmetry within the in‐plane magnetic field, leading to an unbalanced chirality between the left‐handed and right‐handed Bloch walls. These new results foster a better understanding of the chiral domain properties within a magnetic field.

Giant Asymmetry of Domain Walls Propagation in Pd/Co/Pd(111) Epitaxial Structures with Different Interface Roughness

“…However, in some papers, the asymmetrical v ( H x ) curves keeping strong asymmetry in the entire range of the IP magnetic fields were observed. Such asymmetrical v ( H x ) curves were observed in polycrystalline Pt/Co/Pt ,, and Ir/Co/Pt systems and in an epitaxial Pd/Co/Pd(111) system . In our previous paper, we showed that the asymmetric velocity curves of the same shape could not only be caused by the DMI but also the chiral damping effect should be taken into consideration.…”

“…According to the generally accepted definition of the homochiral Neél DWs, in large positive IP fields, H x ≫ |H D ± H B |, DW from the left (right) side of the circular domain with positive magnetization has left-handed ↓ → ↑ (righthanded ↑ → ↓) chirality. 46,47 The relation…”

“…According to the generally accepted definition of the homochiral Néel DWs, in large positive IP fields, H x ≫ | H D ± H B |, DW from the left (right) side of the circular domain with positive magnetization has left-handed ↓ → ↑ (right-handed ↑ → ↓) chirality. , The relation A = v ↑↓ ( H x )/ v ↓↑ ( H x ) in H x ≫ | H D ± H B | reflects the asymmetry between the velocities of DWs of opposite chirality. Taking into account the fact that end points of DWs of a circular domain are considered, hence θ ≈ 0 (see Figure S4, for large IP magnetic fields, this assumption is well fulfilled), and the asymmetry between the velocities of right-handed and left-handed DWs induced by DMI tends to zero in large IP positive magnetic fields (in which DWs are in the Néel state), the asymmetry coefficient calculated for the large IP magnetic fields is directly related to the chiral damping weight according to the expression A sat ( H x ≫ 0 ) = v 0 false↑ false↓ ( ϕ = 0 , θ = 0 ) v 0 false↓ false↑ ( ϕ = 0 , θ = ) = v 0 * ( 1 − α cd ) v 0 * ( 1 + α cd ) = 1 − α cd 1 + α cd The energy of the effective interfacial DMI, denoted as D eff , was quantified using Brillouin–Mandelstam light scattering (BLS) spectroscopy in the Pd(3) and Pd(12.5) samples (as discussed in Section S5).…”

“…The DMI strongly influences the dynamics of DWs in systems with PMA both under an impact of driving magnetic fields and currents. , The effect of DMI on the structure of DWs may be considered as an inclusion of an effective homochiral IP magnetic field, H DMI , oriented along the normal to the surface of DWs and acting on the DWs. , The application of an external magnetic field or its emulation by an interlayer magnetic coupling between layers breaks the rotational symmetry of the system. , Opposite DWs, which are orthogonal to the external IP magnetic field, possess different surface energies. It was stated that in a low-speed creep regime, the velocity of DWs is generally defined by their energy .…”

Tunable Magnetic Domain Patterns in Thickness-Gradient Nickel Films on Flexible PDMS Substrates

“…Many techniques have been developed to modulate the magnetic domain patterns. For example, the chiral domains of magnetic films can be regulated by an applied magnetic field . The direction of stripe domains can be controllably changed by an applied current based on the interaction between spin waves and domain walls. , The distribution of magnetic domains can also be regulated by changing the temperature .…”