Experimental Evidence for Nonspherical Magnetic Form Factor in Ru3+: Article No. 104432

Colin Sarkis, John Villanova, Casey Eichstaedt, Adolfo Eguiluz, Jaime Fernandez-Baca, Masaaki Matsuda, Jiaqiang Yan, Christian Balz, Arnab Banerjee, D. Alan Tennant, Tom Berlijn, Stephen Nagler

Research output: Contribution to journalArticlepeer-review


The Mott insulator ..alpha..-RuCl3 has generated great interest in the community due to its possible field-induced Kitaev quantum spin liquid state. Despite enormous effort spent trying to obtain the form of the low-energy Hamiltonian, there is currently no agreed upon set of parameters which is able to explain all of the data. A key piece of missing information lies in the determination of the magnetic form factor of Ru3+, particularly for a true quantitative treatment of inelastic neutron scattering data. Here we present the experimentally derived magnetic form factor of Ru3+ in the low spin 4d5 state using polarized neutron diffraction within the paramagnetic regime on high-quality single crystals of ..alpha..-RuCl3. We observe strong evidence of an anisotropic form factor, expected of the spin-orbit coupled jeff=12 ground state. We model the static magnetization density in increasing complexity from simple isotropic cases, to a multipolar expansion, and, finally, ab initio calculations of the generalized jeff=12 ground state. Comparison of both single ion models and inclusion of Cl- anions support the presence of hybridization of Ru3+ with the surrounding Cl- ligands.
Original languageAmerican English
Number of pages18
JournalPhysical Review B
Issue number10
StatePublished - 2024

NREL Publication Number

  • NREL/JA-5K00-89612


  • crystal-field theory
  • form factors
  • magnetism
  • neutron scattering


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