Searching for topological spin textures in a noncentrosymmetric antiferromagnet

Topological spin textures (TSTs) such as magnetic skyrmion have attracted a lots of attentions. The search of TSTs in f-electron systems have led to quite some new discoveries, in particular in some Eu- and Gd- based compounds. We have grown high-quality single crystal and polycrystalline samples of EuPtAs with a tetragonal polar structure, and have constructed the field--temperature phase diagram. One of the field-induced phase (phase III) show evidence of topological Hall effect. The zero field magnetic stucture is refined to be a cyclodial structure. Here we propose to measure single crystal neutron diffraction at WISH, with magnetic fields applied along the c-axis, to check if there is TST inside phase III, and to map the evolution of the magnetic structure with field.