Fig. 2: DMI modulation on the engineered surfaces.
a Sketch of the local chirality control via an inhomogeneous surface. b LEEM image of the morphology of Pd stripes grown on W(110) surface; 1 ML and 0 ML Pd regions are shown in red and blue, respectively (imaging condition: 1.5 eV). c Compound SPLEEM image of perpendicularly magnetized domain structures of [Ni(2.1 ML)/Co(1 ML)]2 grown on the Pd stripes with alternating thickness of 1.9 ML and 2.9 ML on W(110) substrate (Method), where the black arrows and the color wheel highlight the spin inside the domain walls. d Derived Néel-chirality within the domain walls is highlighted by the thin, colourized lines, which are superimposed onto the LEEM image of Pd film thickness in (b). L.N., B., and R.N. stand for the left-handed Néel, Bloch, and right-handed Néel, respectively. e Simulated domain walls’ Néel-chirality on surfaces with DMI regions with opposite signs, input by b. Positive DMI corresponds to left-handed chirality. f Experimental statistics on the dependence of α on LDW. The inset is a schematic diagram defining α. m is the measured magnetization unit vector. mNéel is the expected magnetization unit vector in Néel DW controlled by engineered-DMI. LDW is the length of DW within the DMI region of the same sign. g Monte-Carlo simulated phase diagram in \({L}_{{{{\rm{DW}}}}}-{D}_{{ij}}\) space, where \({w}_{{{{\rm{DW}}}}}\) is the width of the domain wall, J is the strength of symmetric exchange interaction, and \({D}_{{ij}}\) is the strength of the DMI. The strength of the Bloch/Néel component is defined by the color bar. The orange dashed line represents the result of the analytical model of the boundary between alternating Néel domain walls and uniform Bloch domain walls.
