Electronic structure of the electron-doped Ca${}_{0.86}$Pr${}_{0.14}$MnO${}_3$

We have studied the temperature-dependent changes in the near $E_F$ electronic structure of the electron-doped, phase separated colossal magnetoresistance (CMR) compound, Ca${}_{0.86}$Pr${}_{0.14}$MnO${}_3$ using photoemission and x-ray absorption studies. At low temperatures, this compound shows a high $e_g$ electron density near the $E_F$ though the compound is insulating. Photoemission measurements further showed a temperature dependence of the $e_g$ electron occupation and localization while the complementary results of XAS showed corresponding changes in the number of unoccupied states. Our results indicate a transfer of charges from the $t_{2g}$ states to the $e_g$ band, probably due to a decrease in the crystal field splitting in the ferromagnetic metallic (FMM) phase following the structural changes of the MnO${}_6$ octahedra at low temperatures. We have interpreted our results from a FMM-antiferromagnetic insulating (AFMI) phase separation scenario.

Figure 1

The resistivity vs temperature curve of Ca${}_{0.86}$Pr${}_{0.14}$MnO${}_3$.

Figure 2

The angle-integrated valence-band photoemission spectrum of Ca${}_{0.86}$Pr${}_{0.14}$MnO${}_3$ taken by using 124 eV photons. The spectra taken at different temperatures (30, 70, 110, 220, and 300 K) are normalized for their intensities and shifted along $y$ axis by a constant for clarity of presentation.

Figure 3

The near $E_F$ region of the valence band spectra (with higher resolution) of ${}_{0.86}$Pr${}_{0.14}$MnO${}_3$ taken at temperatures 30, 70, 110, 220, and 300 K. This feature refers to the Mn $3d{e}_{g\uparrow }$ occupied states.

Figure 4

The O K-edge x-ray absorption spectra of the Ca${}_{0.86}$Pr${}_{0.14}$MnO${}_3$ taken at 30, 80, 150, 200, and 300 K. The pre-edge feature appears between 527–533 eV is mostly due to the strong hybridization between Mn $3d$ and O $2p$ orbitals.

Figure 5

The pre-edge peak of the O K-edge XAS spectra of Ca${}_{0.86}$Pr${}_{0.14}$MnO${}_3$ taken at temperatures 30, 80, 150, 200, and 300 K.