Resonant x-ray scattering study of diffuse magnetic scattering from the topological semimetals EuCd2As2 and EuCd2Sb2

We have investigated the magnetic correlations in the candidate Weyl semimetals ${\mathrm{EuCd}}_{2}P{n}_{2}$ ($Pn=\mathrm{As}$, Sb) by resonant elastic x-ray scattering at the ${\mathrm{Eu}}^{2+}$ ${M}_{5}$ edge. The temperature and field dependence of the diffuse scattering of ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$ provide direct evidence that the Eu moments exhibit slow ferromagnetic (FM) correlations well above the N\'eel temperature. By contrast, the diffuse scattering in the paramagnetic phase of isostructural ${\mathrm{EuCd}}_{2}{\mathrm{Sb}}_{2}$ is at least an order of magnitude weaker. The FM correlations present in the paramagnetic phase of ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$ could create short-lived Weyl nodes.