Comparison of the temperature-dependent electronic structure of the perovskites)

The electronic band structure and the local screening effects of the transition-metal perovskites (Formula presented) ((Formula presented)) 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 (Formula presented) and (Formula presented) bands of (Formula presented)(Formula presented)Mn(Formula presented) 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 (Formula presented)(Formula presented)Mn(Formula presented). The changes in local screening across the Curie temperature were substantially larger for (Formula presented)(Formula presented)Mn(Formula presented) than for (Formula presented)(Formula presented)Mn(Formula presented). This is consistent with the less itinerant band structure of (Formula presented)(Formula presented)Mn(Formula presented), as compared to the highly dispersive bands of (Formula presented)(Formula presented)Mn(Formula presented). These results suggest that there is less hybridization in (Formula presented)(Formula presented)Mn(Formula presented), as compared to (Formula presented)(Formula presented)Mn(Formula presented). The results point to greater electron localization in the (Formula presented)(Formula presented)Mn(Formula presented) compound.