The structure and electronic transport properties of hole-doped ${\mathrm{La}}_{3/4}{\mathrm{Ca}}_{1/4}{\mathrm{MnO}}_3$ perovskite have been investigated as a function of pressure up to about 15 GPa. Though the applied pressure enhances the electrical conductivity, the high-pressure resistivity data point out a competing mechanism interfering with the pressure-induced charge delocalization that prevent the system from reaching a fully metallic state around room temperature. X-ray diffraction results reveal unexpected structural modifications with increasing pressure that can be interpreted with changes in the coherence length of the Jahn-Teller distortions.

• Received 29 May 2001

DOI:https://doi.org/10.1103/PhysRevB.65.012111