Single- and Multimagnon Dynamics in Antiferromagnetic $\alpha$-Fe${}_2$O${}_3$ Thin Films

Abstract

Understanding the spin dynamics in antiferromagnetic (AFM) thin films is fundamental for designing novel devices based on AFM magnon transport. Here, we study the magnon dynamics in thin films of AFM $S=5/2$ $\alpha$-Fe${}_2$O${}_3$ by combining resonant inelastic x-ray scattering, Anderson impurity model plus dynamical mean-field theory, and Heisenberg spin model. Below 100 meV, we observe the thickness-independent (down to 15 nm) acoustic single-magnon mode. At higher energies (100-500 meV), an unexpected sequence of equally spaced, optical modes is resolved and ascribed to $\Delta S_z=1$, 2, 3, 4, and 5 magnetic excitations corresponding to multiple, noninteracting magnons. Our study unveils the energy, character, and momentum-dependence of single and multimagnons in $\alpha$-Fe${}_2$O${}_3$ thin films, with impact on AFM magnon transport and its related phenomena. From a broader perspective, we generalize the use of L-edge resonant inelastic x-ray scattering as a multispin-excitation probe up to $\Delta S_z=2S$. Our analysis identifies the spin-orbital mixing in the valence shell as the key element for accessing excitations beyond $\Delta S_z=1$, and up to, e.g., $\Delta S_z=5$. At the same time, we elucidate the novel origin of the spin excitations beyond the $\Delta S_z=2$, emphasizing the key role played by the crystal lattice as a reservoir of angular momentum that complements the quanta carried by the absorbed and emitted photons.

Accepted in Physical Review X

References in corpus (8)

• Spin excitations in a single La${}_2$CuO${}_4$ layer
• Pressure-Driven Metal-Insulator Transition in Hematite from Dynamical Mean-Field Theory
• EDRIXS: An open source toolkit for simulating spectra of resonant inelastic x-ray scattering
• Direct Imaging of Electrical Switching of Antiferromagnetic Néel Order in $\alpha$-Fe${}_2$O${}_3$ Epitaxial Films
• Quadrupolar magnetic excitations in an isotropic spin-1 antiferromagnet
• X-ray spectroscopy of rare-earth nickelate LuNiO${}_3$: LDA+DMFT study
• Electronic Excitations of Hematite Heteroepitaxial Films Measured by Resonant Inelastic X-Ray Scattering at the Fe L-edge
• Site-specific electronic and magnetic excitations of the skyrmion material Cu${}_2$OSeO${}_3$

Cited by in corpus (7)

• Exploring Quantum Materials with Resonant Inelastic X-Ray Scattering
• Altermagnetic splitting of magnons in hematite ($\alpha$-Fe${}_2$O${}_3$)
• Circular Dichroism in Resonant Inelastic X-ray Scattering: Probing Altermagnetic Domains in MnTe
• A compact approach to higher-resolution resonant inelastic X-ray scattering detection using photoelectrons
• Polarization dependency in Resonant Inelastic X-Ray Scattering
• Hidden covalent insulator and spin excitations in SrRu${}_2$O${}_6$
• Hamiltonian parameter inference from resonant inelastic x-ray scattering with active learning