Electronic transition in ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{TiO}}_3$

The transition with increasing x in ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{TiO}}_3$ from an antiferromagnetic, p-type polaronic conductor to an n-type metal with an enhanced Pauli paramagnetism was investigated by monitoring changes in structure, magnetic properties, and, under different hydrostatic pressures, the resistance and thermoelectric power of ceramic samples. We conclude that ${\mathrm{LaTiO}}_3$ is an itinerant-electron antiferromagnet and the transition is first order with a phase separation associated with cooperative oxygen-atom displacements that segregate strongly correlated states from Fermi-liquid states. The Néel temperature $T_N\approx 145\mathrm{K}$ decreases precipitously to 100 K at the phase limit $x=0.045\mathrm{}\pm 0.005;$ the two-phase domain extends over the compositions $0.045<~x<~\mathrm{0.08.}$