Fig. 2: Heat current-driven ordering of a double q-vector helical state to a single q-vector alignment at zero field.

LTEM micrographs of the (a) initial double q-vector helical state at \(295\ {{{{{\rm{K}}}}}}\), (b) paramagnetic state during the application of \({{{{{\boldsymbol{\nabla }}}}}}{T}\, \approx \, 4.2\ {{{{{\rm{K}}}}}}\; {{\upmu}}{{{{{{\rm{m}}}}}}}^{-1}\) which causes an increase in the base temperature to between \(369\ {{{{{\rm{K}}}}}}\) and \(382\ {{{{{\rm{K}}}}}}\) in the field of view and (c) resulting single q-vector helical state upon termination of the heater current and cooling of the field of view to a uniform \(295\ {{{{{\rm{K}}}}}}\) in \(\approx \, 1\ {{{{{\rm{s}}}}}}\). The inset outlined by dashed red lines in (b) is a scanning electron micrograph taken with a \(52^\circ\) sample tilt and indicates the field of view (\(3.2\times 3.2\ {{\upmu}}{{{{{{\rm{m}}}}}}}^{2}\), outlined by dashed black lines) of the experiment (a–c), in which \(T \, > \, {T}_{C}\). Micromagnetic simulations of \({{{{{\boldsymbol{\nabla }}}}}}T\)-driven ordering of the magnetic domains from the (d) initial double q-vector helical state to a (e) paramagnetic state during the application of scaled temperature gradient \({{{{{\boldsymbol{\nabla }}}}}}{T}_{1}^{*}=442\ {{{{{\rm{K}}}}}}\; {{\upmu}}{{{{{{\rm{m}}}}}}}^{-1}\), (f) partially aligned double q-vector helical state during the application of \({{{{{\boldsymbol{\nabla }}}}}}{T}_{2}^{*}=4.4\ {{{{{\rm{K}}}}}}\, {{\upmu}}{{{{{{\rm{m}}}}}}}^{-1}\) and (g) resulting single q-vector helical state after applying \({{{{{\boldsymbol{\nabla }}}}}}{T}_{2}^{*}\) for a sufficiently long time. A magnetic defect in the helical state shown in (f) is indicated by an arrow. The heater is located on the right-hand-side of each image, while the cold bath is on the left-hand-side. Scale bars are \(1\ {{\upmu}}{{{{{\rm{m}}}}}}\) in (a–c) and \(10\ {{\upmu}}{{{{{\rm{m}}}}}}\) in the inset in (b).