Observation of Néel-type skyrmions in Mn_2-xZn_xSb single crystals.

Mn_2-xZn_xSb alloys are layered tetragonal materials for which previous work has suggested they exhibit tuneable nontrivial topological magnetism [1]. While the parent compound has a centrosymmetric tetragonal lattice and ferrimagnetic order, with high Zn doping a layered structure and ferromagnetic order develops. We have studied single crystals with high Zn doping (x = 0.81, 0.85) with magneto-optical Kerr effect (MOKE) microscopy and Lorentz TEM as a function of temperature. We observe magnetic stripe domains at low field that evolve into skyrmions at higher field. Lorenz TEM imaging determined that they are Néel-type skyrmions, which is not commonly observed in bulk materials. There is no significant change in the domain behavior, even when passing the spin-reorientation transition [1] indicating that the out-of-plane magnetic component still dominates at low temperatures.

[1] Md Rafique Un Nabi et al., Phys. Rev B 104, 174419 (2021).