C-type antiferromagnetic structure of topological semimetal CaMnSb${}_2$

Abstract

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 $T{}_{\mathrm{N}}$ = 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 $P{n}^{\prime }{m}^{\prime }{a}^{\prime }$, 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.

7 Pages, 6 figures

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