Spontaneous Asymmetry of Chiral Magnetic Domains Within a Magnetic Field

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.