Magnetotransport properties of BaMn$_2$Pn$_2$ compounds

We report interesting magnetotransport properties observed in BaMn$_2$Pn$_2$ (BMPn, with Pn = As, Sb, Bi) systems. BMPn materials have the same layered crystal structure with that of BaFe$_2$As$_2$, one of the parent compounds for iron-based superconductors. The large Hund's coupling in the half-filled $3d^5$ orbitals promotes a localized high spin state of Mn$^{2+}$ ions and results in a G-type antiferromagnetic insulator with a fairly high $T_{\mathrm{N}}$ [1, 2]. Our experiments show that the resistivities in all BMPn's have complex dependencies on both temperature and magnetic field. Measurements of resistivity under magnetic fields indicate sizable and anisotropic magnetoresistance that vary strongly with temperature. On the other hand, a detailed analysis of the temperature dependencies of the resistivity indicates a transition-like feature at which the behaviors of magnetoresistance and Hall effect completely change. Interestingly, by changing the pnictide site in BMPn from As to Bi, the features of the magnetotransport properties are systematically varied.\\ 1. Singh \emph{et al}, PRB 79, 2, (2009).\\ 2. McNally \emph{et al}, PRB 92, 115142 (2015).