We present inelastic neutron scattering measurements of magnetic excitations in stripe ordered ${\mathrm{Pr}}_{3/2}{\mathrm{Sr}}_{1/2}{\mathrm{NiO}}_4$ at $T\sim 10\mathrm{K}$. For the observed magnetic incommensurability $\epsilon =0.4$, we have incorporated a stripe discommensuration model in our linear spin wave calculation and obtained best agreement with the measured spin wave dispersion, especially to explain the symmetrical outward shift of the magnetic peaks from Néel ordered zone center in energy range 35 to 45 meV. Our study indicates the prerequisite to consider a discommensurated spin stripe unit with proper out-of-plane and in-plane exchange interactions in between ${\mathrm{Ni}}^{2+}$ spins to describe the observed spin wave characteristics in ${\mathrm{Pr}}_{3/2}{\mathrm{Sr}}_{1/2}{\mathrm{NiO}}_4$.

• Received 14 June 2019
• Revised 15 February 2020
• Accepted 12 March 2020

DOI:https://doi.org/10.1103/PhysRevLett.124.147202