Direct observation of cycloidal spin modulation and field-induced transition in N\'eel-type skyrmion-hosting VOSe$_2$O$_5$

TL;DR

This study uses polarized small-angle neutron scattering to directly observe cycloidal spin modulation and field-induced phase transitions in VOSe2O5, revealing detailed magnetic structures of skyrmions in this material.

Contribution

The paper provides the first direct neutron scattering evidence of cycloidal spin modulation in VOSe2O5 and explores field-induced magnetic phases, including a possible double-q state.

Findings

Confirmed cycloidal spin modulation in all incommensurate phases.

Identified a field-induced incommensurate phase near the skyrmion state.

Proposed the possibility of an anisotropic double-q spin structure.

Abstract

We investigate the spin rotational structure of magnetic skyrmions in a tetragonal polar magnet VOSe2O5 via polarized small-angle neutron scattering (SANS). Spin polarization analysis of the scattered neutrons provides consistent evidence for the cycloidal spin modulation in all the incommensurate phases at zero and non-zero magnetic field along the c axis, including the triangular skyrmion-lattice phase. In the vicinity of the skyrmion phase, we performed extensive SANS measurements to unravel a field-induced incommensurate phase (IC-2 state). We discuss the possibility of anisotropic double-q state as an alternative spin structure to provisional square skyrmion-lattice state.