We have measured the O-isotope effects on the magnetic and electrical properties of (Formula presented) under hydrostatic pressure up to 1.9 GPa. The pressure was found to reversibly enhance the metal-insulator transition temperature (Formula presented) and suppress the resistivity (Formula presented) of both isotopic samples, but at different rates, depending on the O-isotopic mass of the samples. It was also found that pressure suppresses the isotope effect linearly, while the (Formula presented) exchange drastically enhances (Formula presented) The greater (Formula presented) and (Formula presented) observed in the (Formula presented) sample can be understood qualitatively in terms of the double exchange interaction between Mn ions and the band reduction effect of polarons, but the (Formula presented) difference is much greater than predicted. The discrepancy suggests that modifications may be needed for the model.
|Physical Review B - Condensed Matter and Materials Physics
|Published - 1999
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics