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Spin-orbital order and excitons in magnetoresistive HoBi



Jonathan N. Gaudet, H. Yang, E. Smith, T. Halloran, J. Clancy, Jose Rodriguez Rivera, Guangyong Xu, Yang Zhao, Wangchun Chen, G. Sala, Adam A. Aczel, B. Gaulin, Fazel Tafti, Collin L. Broholm


The magnetism of the rock-salt fcc rare-earth monopnictide HoBi, a candidate topological material with extreme magnetoresistance, is investigated. From the Ho3+ non-Kramers J=8 spin-orbital multiplet, the cubic crystal electric field yields six near degenerate low energy levels. These constitute an anisotropic magnetic moment with a Jahn-Teller-like coupling to the lattice. In the cubic phase for T > 5.72(1) K, the paramagnetic neutron scattering is centered at k = (1/2 1/2 1/2) indicating dominant antiferromagnetic interactions between Ho spins separated by 100} and ferromagnetic interactions between spins displaced by 1/2 1/2 0}. For T < TN, a type-II AFM long-range order with k = (1/2 1/2 1/2) develops along with a tetragonal lattice distortion. While neutron diffraction from a multi-domain sample cannot unambiguously determine the spin orientation within a domain, the bulk magnetization, structural distortion, and our measurements of the magnetic excitations however, show the easy axis coincides with the tetragonal axis. The weakly dispersive excitons for T < TN can be accounted for by a spin Hamiltonian that includes the crystal electric field and exchange interactions within the Random Phase Approximation.
Physical Review B


Neutron Diffraction, Inelastic Neutron Scattering, X-ray Diffraction, Magnetic excitons, Extreme Magnetoresistance


Gaudet, J. , Yang, H. , Smith, E. , Halloran, T. , Clancy, J. , Rodriguez Rivera, J. , Xu, G. , Zhao, Y. , Chen, W. , Sala, G. , Aczel, A. , Gaulin, B. , Tafti, F. and Broholm, C. (2023), Spin-orbital order and excitons in magnetoresistive HoBi, Physical Review B, [online],, (Accessed April 23, 2024)
Created March 22, 2023, Updated March 21, 2024