Comparison of the temperature-dependent electronic structure of the perovskites La\u3csub\u3e0.65\u3c/sub\u3eCa\u3csub\u3e0.35\u3c/sub\u3eMnO\u3csub\u3e3\u3c/sub\u3e (A=Ca, Ba)

The electronic band structure and the local screening effects of the transition-metal perovskites La0.65A0.35MnO3 (A=Ba and Ca ) have been examined across the coupled magnetic-metallic phase transition using the techniques of angle-resolved photoemission, resonance photoemission, and inverse photoemission. Temperature-dependent band shifts of the eg and t2g bands of La0.65Ca0.35MnO3 have been observed. These changes in the observed electronic structure correlate with the phase transition, and are in qualitatively agreement with the predicted behavior associated with double exchange coupled with a dynamic Jahn-Teller distortion. Similar shifts were not observed for La0.65Ba0.35MnO3. The changes in local screening across the Curie temperature were substantially larger for La0.65Ca0.35MnO3 than for La0.65Ba0.35MnO3. This is consistent with the less itinerant band structure of La0.65Ca0.35MnO3, as compared to the highly dispersive bands of La0.65Ba0.35MnO3. These results suggest that there is less hybridization in La0.65Ca0.35MnO3, as compared to La0.65Ba0.35MnO3. The results point to greater electron localization in the La0.65Ca0.35MnO3 compound