Identification of hidden orbital contributions in the ${\mathrm{La}}_{0.65}{\mathrm{Sr}}_{0.35}{\mathrm{MnO}}_3$ valence band

Hybridization of electronic states and orbital symmetry in transition metal oxides are generally considered key ingredients in the description of both their electronic and magnetic properties. In the prototypical case of ${\mathrm{La}}_{0.65}{\mathrm{Sr}}_{0.35}{\mathrm{MnO}}_3$ (LSMO), a landmark system for spintronics applications, a description based solely on Mn $3d$ and O $2p$ electronic states is reductive. We thus analyzed elemental and orbital distributions in the LSMO valence band through a comparison between density functional theory calculations and experimental photoelectron spectra in a photon energy range from soft to hard x rays. We reveal a number of hidden contributions, arising specifically from La $5p$, Mn $4s$, and O $2s$ orbitals, considered negligible in previous analyses; our results demonstrate that all these contributions are significant for a correct description of the valence band of LSMO and of transition metal oxides in general.

Figure 1

Valence band SXPES and HAXPES spectra from LSMO taken at a temperature of $T=200$ K at different photon energies. Capital letters indicate the main structures of the spectra and are discussed in the text.

Figure 2

Total DOS (a) and orbitally projected DOS calculated for lanthanum (b), strontium (c), manganese (d), and oxygen (e) in the LSMO compound.

Figure 3

Atomic per electron photoionization cross section values for the different valence band orbitals and the different LSMO elements, namely La and Sr (a) and Mn and O (b), versus photon energy. Different colors indicate different elements, while different symbols refer to different orbitals, namely $s$ (triangles), $p$ (circles), and $d$ (asterisks). Dashed rectangles outline the cross section values for the photon energy of 1.0 keV, 2.5 keV, and 5.94 keV used for exciting the experimental spectra. In the inset of both panels the trend of the asymmetry parameter $\beta$ versus photon energy is also shown.

Figure 4

Electronic charge for each element and each orbital. The shaded area correspond to the fraction of charge outside the atomic spheres.

Figure 5

Comparison of the calculated DOS (black lines) with the experimental spectra for $h\nu =1.0$ keV, $h\nu =2.5$ keV, and $h\nu =5.94$ keV.

Figure 6

Calculated PDOSs are shown unscaled (a) and weighted (b)–(d) according to the procedure described in the text.