Annealing and pressure effects on structural and ferromagnetic transitions of ${\mathrm{La}}_{0.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{MnO}}_3$ single crystals

A detailed study of annealing and pressure effects on structural phase-transition temperature (${\mathrm{T}}_{\mathrm{s}}$) and ferromagnetic transition temperature (${\mathrm{T}}_{\mathrm{c}}$) was investigated for single crystal ${\mathrm{La}}_{0.85}$ ${\mathrm{Sr}}_{0.15}$ ${\mathrm{MnO}}_3$. ${\mathrm{T}}_{\mathrm{s}}$ and ${\mathrm{T}}_{\mathrm{c}}$, respectively, decrease and increase with increasing pressure and annealing time, which indicated that the lattice distortion is relaxed and the double-exchange interaction is enhanced by annealing and pressure. Three states, orthorhombic phase state, orthorhombic and rhombohedral phases coexisting state, and rhombohedral phase state, can be induced by controlling annealing time at high temperature and by hydrostatic pressure. In the ${\mathrm{La}}_{0.85}$ ${\mathrm{Sr}}_{0.15}$ ${\mathrm{MnO}}_3$ compound, ${\mathrm{T}}_{\mathrm{c}}$ was found to increase about 15 K when the orthorhombic phase transforms to the rhombohedral phase.