Néel-type skyrmion lattice in tetragonal polar magnet VOSe₂O₅

VOSe₂O₅ has been known to form a tetragonal polar lattice with the space group P4cc and to exhibit a ferrimagnetic-like transition at T_C = 7.5 K [1-3]. We synthesized the single crystals and performed the detailed magnetization study to reveal the versatile magnetic phases in a low-field region (H < 100 Oe) including the “A phase” close to the T_C. We perform the SANS investigation and obtain the experimental evidence for the phase transition between cycloidal helimagnetic phase and the triangular skyrmion-lattice phase to demonstrate the Neel-type skyrmion lattice formation in the present system. We identified another magnetic phase of an incommensurate spin texture at lower temperatures under a finite magnetic field, tentatively assigned to a square skyrmion-lattice phase. These findings exemplify the versatile features of Néel-type skyrmions in bulk materials, and provide a further opportunity to explore the physics of topological spin textures in polar magnets.
[1] S.-H. Kim, et al., Chem. Mater. 22, 5074 (2010).
[2] P. G. Meunier et al., Acta Cryst. B30, 2834 (1974).
[3] J.-C. Trombe et al., Nouv. J. Chimie, 11, 321 (1987).