Structure analysis and measurement of resistivity under both isostatic pressure smaller than 1.1 GPa and magnetic field of 1 T were carried out for rhombohedral ${\mathrm{La}}_{1\mathrm{-}\mathit{x}}$${\mathit{A}}_{\mathit{x}}$${\mathrm{MnO}}_3$ (A=Na, K, Rb, and Sr). A close relationship was confirmed to hold between ${\mathit{T}}_{\mathit{c}}$ and the bond distance of Mn-O. The application of the isostatic pressure up to 1.1 GPa decreased the resistivity more than 60% below ${\mathit{T}}_{\mathit{c}}$ but this effect was smaller above ${\mathit{T}}_{\mathit{c}}$. This pressure dependency was explained by the decrease in bond distance of Mn-O under pressure. Magnetic resistance for ${\mathrm{La}}_{0.87}$${\mathrm{K}}_{0.06}$${\mathrm{Mn}}_{0.97}$${\mathrm{O}}_3$ was found to be -10%/T, which is the same order of the previous reports for ${\mathrm{La}}_{1\mathrm{-}\mathit{x}}$${\mathit{A}}_{\mathit{x}}$${\mathrm{MnO}}_3$ (A=Ca, Sr, Ba).

• Received 22 June 1995

DOI:https://doi.org/10.1103/PhysRevB.52.12522