Imaging of 3dMn orbitals in the ferromagnetic state for Ca-substituted manganite: Magnetic Compton investigation

Abstract

The 3$d$ Mn orbitals in Pr${}_{0.25}$Ca${}_{0.25}$MnO${}_{3}$ (PCMO), in the ferromagnetic phase, were imaged by two-dimensional reconstruction of spin-polarized electron-momentum density projected along the [100] and [110] principal directions. The results were analyzed using a molecular-orbital scheme to understand the population distribution for the ${t}_{2g}$ and the ${e}_{g}$ states for Mn. The analysis shows that the ${t}_{2g}$ states are found to be half-filled, whereas, the ${e}_{g}$ states are dominated mainly by ${x}^{2}\ensuremath{-}{z}^{2}$-type orbitals for both projected [100] and [110] principal directions. The observance of preferential filling of the ${x}^{2}\ensuremath{-}{z}^{2}$-orbital type is consistent with a cooperative Jahn-Teller distortion of the MnO${}_{6}$ octahedra leading to a local tetragonal compression along the $y$ axis for this system. As a result of this distortion, the 3${y}^{2}\ensuremath{-}{r}^{2}$-type orbitals have a small population for PCMO; the ratio of the ${x}^{2}\ensuremath{-}{z}^{2}$-type orbitals to that of the 3${y}^{2}\ensuremath{-}{r}^{2}$-type orbitals is greater than 2, similar to that seen for bilayered manganites.