Fig. 3: Unidirectional transformation of topological spin textures at zero field via heat current.
From: Heat current-driven topological spin texture transformations and helical q-vector switching
a LTEM micrograph of the initial magnetic state composed of metastable spin textures stabilized by applying \({B}_{z}\) to form a Sky lattice state and then reducing the field to zero at \(295\ {{{{{\rm{K}}}}}}\) (schematic on LHS of a), after which some skyrmions remained stable. LTEM micrographs of the zero-field magnetic states taken after heater current applications of (b) \({{{{{\boldsymbol{\nabla }}}}}}{T}=2.0\ {{{{{\rm{K}}}}}}\, {{\upmu}}{{{{{{\rm{m}}}}}}}^{-1}\) (\(314\ {{{{{\rm{K}}}}}} \, < \, {T}_{{{{{{{\rm{FOV}}}}}}}} \, < \, 323\ {{{{{\rm{K}}}}}},\,{{{{{\rm{where}}}}}}\,{T}_{{{{{{{\rm{FOV}}}}}}}}\) is the temperature in the field of view) and (c) \({{{{{\boldsymbol{\nabla }}}}}}{T}=5.2\ {{{{{\rm{K}}}}}}\, {{\upmu}}{{{{{{\rm{m}}}}}}}^{-1}\) (\(343\ {{{{{\rm{K}}}}}} \, < \, {T}_{{{{{{{\rm{FOV}}}}}}}} \, < \, 368\ {{{{{\rm{K}}}}}}\)) lasting \(15\ {{{{{\rm{s}}}}}}\) (except for those values noted in the “Methods”). Selected spin textures are marked as they transform from Sky (blue arrows) to NTBs (green arrows) to Askys (red arrows). d Spin texture population (\({{{{{{\rm{N}}}}}}}_{{{{{{\rm{ST}}}}}}}\) is the combined number of antiskyrmions Asky, nontopological bubbles NTB, and skyrmions Sky) versus \({{{{{\boldsymbol{\nabla }}}}}}T\) of the full \(7.3\times 5.5\ {{\upmu}}{{{{{{\rm{m}}}}}}}^{2}\) field of view in which the \(4.6\times 4.6\ {{\upmu}}{{{{{{\rm{m}}}}}}}^{2}\) area shown in (a–c) is contained. Five types of spin textures are identified, including Askys (red square markers), horizontal Skys (“H Sky” with open blue triangle markers), vertical skyrmions (“V Sky” with blue, upside-down triangle markers), horizontal non-topological bubbles (“H NTB” with open green equal-length-diagonal rhombus markers), and vertical non-topological bubbles (“V NTB” with green rhombus markers). The total number of spin textures is plotted by a solid black line with open circular markers. The inset panel shows the field of view of the experiment within the (Fe0.63Ni0.3Pd0.07)3P device, and the right-hand-side legend shows schematics of the in-plane magnetization for each spin texture measured in (a–d). The scale bar in (a–c) is \(1\ {{\upmu}}{{{{{\rm{m}}}}}}\) and \(10\ {{\upmu}}{{{{{\rm{m}}}}}}\) in the inset panel of (d).
