C-type antiferromagnetic structure of topological semimetal CaMnSb\(_2\)

Determination of the magnetic structure and confirmation of the presence or absence of inversion (\(\mathcal{P}\)) and time reversal (\(\mathcal{T}\)) symmetry is imperative for correctly understanding the topological magnetic materials. Here high-quality single crystals of the layered manganese pnictide CaMnSb\(_2\) are synthesized using the self-flux method. De Haas-van Alphen oscillations indicate a nontrivial Berry phase of \(\sim\) \(\pi\) and a notably small cyclotron effective mass, supporting the Dirac semimetal nature of CaMnSb\(_2\). Neutron diffraction measurements identify a C-type antiferromagnetic (AFM) structure below \(T\rm_{N}\) = 303(1) K with the Mn moments aligned along the \(a\) axis, which is well supported by the density functional theory (DFT) calculations. The corresponding magnetic space group is \(Pn'm'a'\), preserving a \(\mathcal{P}\times\mathcal{T}\) symmetry. Adopting the experimentally determined magnetic structure, band crossings near the Y point in momentum space and linear dispersions of the Sb \(5p_{y,z}\) bands are revealed by the DFT calculations. Furthermore, our study predicts the possible existence of an intrinsic second-order nonlinear Hall effect in CaMnSb\(_2\), offering a promising platform to study the impact of topological properties on nonlinear electrical transports in antiferromagnets.