Magnon spectrum of the Weyl semimetal half-Heusler compound GdPtBi

Abstract

The compound GdPtBi is known as a material where the non-trivial topology of electronic bands interplays with an antiferromagnetic order, which leads to the emergence of many interesting magnetotransport phenomena. Although the magnetic structure of the compound has previously been reliably determined, the magnetic interactions responsible for this type of order remained controversial. In the present study, we employed time-of-flight inelastic neutron scattering to map out the low-temperature spectrum of spin excitations in single-crystalline GdPtBi. The observed spectra reveal two spectrally sharp dispersive spin-wave modes, which reflects the multi-domain state of the k = ( 1 2 1 2 1 2 ) face-centred cubic antiferromagnet in the absence of a symmetry-breaking magnetic field. The magnon dispersion reaches an energy of ∼ 1.1 meV and features a gap of ∼ 0.15 meV. Using linear spin-wave theory, we determined the main magnetic microscopic parameters of the compound that provide good agreement between the simulated spectra and the experimental data. We show that GdPtBi is well within the ( 1 2 1 2 1 2 ) phase and is dominated by second-neighbor interactions, thus featuring low frustration.

Anisotropic electrical and thermal magnetotransport in the magnetic semimetal GdPtBi

“…2) in sample 1 could therefore be related and might also explain why the MR of sample 1 exhibits additional features compared to sample 2. Furthermore, frustration might also lead to a field-dependent phonon density [45], however, the moderate frustration of the Gd ions is found to be relieved already by the next-nearest neighbor interactions [38], GdPtBi thus exhibits only low frustration. Magnetostriction might have an effect on the MTR as well.…”

“…It might also be that the dispersion of different magnon branches along certain directions leads to field-dependent transitions. The magnon spectrum of GdPtBi has recently been studied via inelastic neutron scattering [38]. Two modes with similar energy at their minima were revealed, but depending on the direction they disperse quite differently.…”

“…There have been reports on a chiral anomaly-induced negative longitudinal magnetoresistivity [32,33] and anisotropic planar Hall resistivity [34] as well as anomalous features in the Hall [33,35] and (magneto)resistivity [29,32,33,35]. Many studies [25,[36][37][38] have also been carried out on the magnetism of GdPtBi, exploring the antiferromagnetic ordering of the local moments stemming from Gd's half-filled 4 f shell with L = 0 and J = S = 7/2. Furthermore, optical methods have been employed, confirming the presence of electronic bands with nearly linear dispersion [39].…”

Degenerate manifolds, helimagnets, and multi-$\mathbf{Q}$ chiral phases in the classical Heisenberg antiferromagnet on the face-centered-cubic lattice

“…Our work also provides the basis for understanding the origin of a plethora of fcc magnetic structures in wide a variety of magnetic materials [24]. In particular, a recent investigation of the half-Heusler compound GdPtBi [25] proposed an antiferromagnetic J 1 -J 2 -J 3 Heisenberg model, and argued for the indispensability of a J 3 interaction to match the observed neutron scattering profile.…”

Topological signatures in nodal semimetals through neutron scattering

“…These include a theoretical overview on probing bulk excitations in type-I WSMs with unpolarized and polarized neutrons [83] and an experimental study of coupling between Dirac fermions and spin waves [84]. A non-exhaustive compilation of other neutron scattering experiments on topological semimetals (including candidates) up until now can be noted in references [59,77,82,[84][85][86][87][88][89][90][91][92][93]. Although these earlier surveys are encouraging, a great deal of work remains to accentuate the potential usefulness of neutron scattering toward characterizing future TNMs sensitive to topological bands.…”