Antiferromagnetic metallic state in doped manganites

Electronic and magnetic properties are systematically investigated for doped manganites $R_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ $(R={\mathrm{La}}_{1-z}{\mathrm{Nd}}_z)$ by changing the nominal hole concentration $x$ and the averaged ionic radius of the perovskite $A$ site $\mathrm{}\left(z\right),$ or the one-electron bandwidth $W.\mathrm{}$ In the heavily doped region $(x>~0.50),$ we observed a layered-type ($A$-type) antiferromagnetic state with metallic conductivity ($\rho \approx 4\times {10}^{-4}\Omega \mathrm{cm}$ at 5 K for ${\mathrm{La}}_{0.46}{\mathrm{Sr}}_{0.54}{\mathrm{MnO}}_3$). This observation suggests that the antiferromagnetic metallic (AFM) state is the alternative ground state for doped manganites, besides the ferromagnetic metallic (FM) state.