Electronic transition in La_1-xSr_xTiO₃

The transition with increasing x in La_1-xSr_xTiO₃ 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 LaTiO₃ 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≈145K decreases precipitously to 100 K at the phase limit x=0.045±0.005; the two-phase domain extends over the compositions 0.045<~x<~0.08.