Measurements of the transport properties under high pressure of an $x=0.16\mathrm{}$ crystal have revealed the disappearance, in a two-phase domain, of a low-temperature, orbitally ordered $O^{″}$ phase, as well as a discontinuous crossover of the ferromagnetic Curie temperature $T_c$ at an orthorhombic-rhombohedral phase boundary in the narrow compositional range $0.16<x<\mathrm{}0.17\mathrm{}$ of the system ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3.$ The data also suggest that the $O^{″}$ phase below an insulator-metal transition temperature $T_{\mathrm{IM}}$ is distinguishable from that between the order-disorder transition at $T_{\mathrm{oo}}.$

• Received 31 July 2000

DOI:https://doi.org/10.1103/PhysRevB.63.172416