Resonant elastic X-ray scattering (REXS) at the Eu M5 edge reveals an antiferromagnetic structure in layered EuCd2Sb2 at temperatures below TN = 7.4 K with a magnetic propagation vector of (0, 0, 1/2) and spins in the basal plane. Magneto-transport and REXS measurements with an in-plane magnetic field show that features in the magnetoresistance are correlated with changes in the magnetic structure induced by the field. Ab initio electronic structure calculations predict that the observed spin structure gives rise to a gapped Dirac point close to the Fermi level with a gap of ∆E ∼ 0.01 eV. The results of this study indicate that the Eu spins are coupled to conduction electron states near the Dirac point.

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Spin waves in ferromagnetic USe have been measured by inelastic neutron scattering. Previous measurements on a multidomain USe sample show that the spin wave branch has a zone center frequency of ≊9 THz, and that the spin waves are intrinsically broad. New measurements on a single domain sample show that, in addition, the spin wave is unpolarized. This behavior is unlike that of a classical ferromagnet, in which the polarization is transverse, but similar to behavior observed in some singlet ground state systems.

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