Possible Mott transition in layeredSr2Mn3As2O2single crystals

Abstract

Single crystals of ${\mathrm{Sr}}_{2}{\mathrm{Mn}}_{3}{\mathrm{As}}_{2}{\mathrm{O}}_{2}$ have been grown for the first time, for which we show a possible layer-selective Mott insulator behavior. This compound stands out as a hybrid structure of ${\mathrm{MnO}}_{2}$ and MnAs layers, analogously to the active ${\mathrm{CuO}}_{2}$ and FeAs layers, respectively, in the cuprate and iron-based high-temperature superconductors. Electrical transport, neutron diffraction measurements, together with density functional theory calculations on ${\mathrm{Sr}}_{2}{\mathrm{Mn}}_{3}{\mathrm{As}}_{2}{\mathrm{O}}_{2}$ single crystals converge toward a picture of independent magnetic order at ${T}_{1}\ensuremath{\sim}79$ K and ${T}_{2}\ensuremath{\sim}360$ K for the two Mn sublattices, with insulating behavior at odds with the metallic behavior predicted by calculations. Furthermore, our inelastic neutron-scattering studies of spin-wave dispersions for the Mn(1) sublattice reveal an effective magnetic exchange coupling of $SJ\ensuremath{\sim}3.7$ meV. This is much smaller than those for the Mn(2) sublattice.