Enhanced Néel-type skyrmion stability in polar VOSe₂O₅ through tunable magnetic anisotropy under pressure

Polar VOSe₂O₅, belonging to the P4cc space group (C_4V symmetry), was recently discovered to host a

rare Néel-type skyrmion phase within a very narrow range of temperature and magnetic field. Motivated by

this discovery, we investigated the effect of pressure on its magnetic properties, focusing on improving the

stability of the skyrmion phase. At ambient pressure, two magnetic transitions were observed at T_C1 ∼ 7.4 K and

T_C2 ∼ 4.0 K. Notably, the contrasting behavior of these transitions under applied magnetic fields—TC1 increases,

whereas TC2 is suppressed—reflects the magnetic anisotropy in VOSe₂O₅. Neutron diffraction refinements

revealed a three-up-one-down ferrimagnetic configuration aligned along the b axis at 1.8 K, and an incommen-

surate cycloidal spin structure rotating within the bc plane at 6 K, further demonstrating the intrinsic magnetic

anisotropic in VOSe₂O₅. Pressure-dependent ac susceptibility measurements showed T_C1 increasing by 0.043(3)

K/kbar and T_C2 are decreasing by -0.052 (4) K/kbar, indicating pressure-tunable anisotropy. The field-temperature

(H-T) phase diagram confirms the stabilization of the Néel-type skyrmion phase under 14.21 kbar of pressure,

with its area expanding approximately threefold. These findings underscore the role of pressure in promoting

Néel-type skyrmion stability through modulation of the magnetic anisotropy, offering valuable insights into

tuning topological phases for spintronics and related technological applications.