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

The 3d Mn orbitals in Pr _0.25Ca _0.25MnO 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 x2-z2-type orbitals for both projected [100] and [110] principal directions. The observance of preferential filling of the x2-z2-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 3y2-r2-type orbitals have a small population for PCMO; the ratio of the x2-z2-type orbitals to that of the 3y2-r2-type orbitals is greater than 2, similar to that seen for bilayered manganites.