Ba$_{1-x}$K$_x$Mn$_2$As$_2$: An Antiferromagnetic Local Moment Metal*

The syntheses of K-doped single crystalline $\rm{Ba_{0.984}K_{0.016}Mn_2As_2}$ and polycrystalline $\rm{Ba_{0.95}K_{0.05}Mn_2As_2}$ with the tetragonal ${\rm ThCr_2Si_2}$ structure are reported. Electrical resistivity, heat capacity, magnetic susceptibility, angle-resolved photoemission spectroscopy and neutron diffraction measurements and spin-polarized electronic structure calculations consistently establish that these hole-doped Ba$_{1-x}$K$_x$Mn$_2$As$_2$ samples are antiferromagnetic local-moment metals, in contrast to the parent BaMn$_2$As$_2$ [1-3] which is an antiferromagnetic local-moment semiconductor. This new class of materials bridges the gap between the iron pnictide and cuprate high $T_{\rm c}$ materials. Investigations of the phase diagram of the Ba$_{1-x}$K$_x$Mn$_2$As$_2$ system and other similar systems are underway.\\[4pt] [1] Y. Singh et al., Phys. Rev. B \textbf{79}, 094519 (2009).\\[0pt] [2] Y. Singh et al., Phys. Rev. B \textbf{80}, 100403 (2009).\\[0pt] [3] D. C. Johnston et al., Phys. Rev. B \textbf{84}, 094445 (2011).