Magnons and paramagnons in (111)-oriented thin films of pyrochlore iridates

Rare-earth pyrochlore iridates R₂Ir₂O₇ (e.g., R = Y, rare-earth elements) are an exciting class of quantum materials which exhibit emergent electronic and magnetic phenomena. These materials exhibit all-in-all-out magnetic ground states stabilized by the competition between the Heisenberg antiferromagnetic correlation and Dzyaloshinskii–Moriya interaction. The nature of the magnetism is encoded not only in the magnetic ground state, but also in the magnon quasiparticles, as well as in their evolution across the Neel transition. In this talk, I will present our recent work in fabricating the high quality Y₂Ir₂O₇ thin films and mapping the magnetic excitations with resonant inelastic x-ray scattering (RIXS). The low-temperature magnon dispersion is consistent with an all-in-all-out magnetic ground state. Towards the Neel transition, the magnon gap does not soften with temperature, which we propose as arising from the spin-orbital nature of the isospin. Moreover, a paramagnon excitation persists above T_c = 140K, indicating the presence of small antiferromagnetic domains above T_c.



We acknowledge the support of the Department of Energy under Grant No. DE-SC0012375.