Magnetic and high-pressure magnetotransport properties of cesium-substituted lanthanum calcium manganites

The nature of the double-exchange (DE) interaction in lanthanum manganites is studied through chemical substitutions, Cs for La, and high-pressure mea surements. Static and high-frequency magnetic measurements and high-pressur e electrical transport studies were carried out on bulk polycrystalline and radio-frequency sputtered thin films of La-0.7-(x)Cs(x)Cao(0.3)MnO(3) for x = 0 - 0.1. The samples are found to be cubic. Curie temperature T-c measu rements provide evidence for bond-length-related weakening of DE as x is in creased from 0 to 0.03. For higher x, the bond-angle-related changes lead t o an increase in the strength of DE. High-pressure mangetoresistance data i ndicate both bond length and bond-angle-related increase of 10-20 K/GPa in T-c with pressure, with the largest increase measured for x = 0.03. The rat e of increase in the Curie temperature with pressure decreases with increas ing T-c. Anomalies are observed in the magnetic parameters for x = 0.03. Th e Cs-concentration de pendence of the low-temperature saturation magnetizat ion shows a minimum close to x = 0.03. Ferromagnetic resonance studies at x -band reveal a 5% decrease in the g-value for x = 0.03 relative to the end members (x = 0 and 0.1). The low-field magnetostriction for x = 0.03 indica tes a relatively strong electron-phonon spin coupling compared to neighbori ng compositions.