Strong orbital polarization in orthorhombic ${\text{DyMnO}}_3$: A combined x-ray linear dichroism and ab initio electronic structure study

We present a combined experimental and theoretical study on the $\text{Mn}3d$ orbital occupation in orthorhombic ${\text{DyMnO}}_3$ single crystals. We have observed a very strong polarization dependence in the $\text{Mn}{L}_{2,3}$ x-ray absorption spectra, indicative for a distinct anisotropic orbital occupation. Ab initio electronic-structure calculations clearly infer the existence of a strong orbital polarization in the $e_g$ band with a staggered $d_{3x^2-r^2}/d_{3y^2-r^2}$-type ordering pattern in the $ab$ plane. This finding is in excellent agreement with a quantitative analyis of the spectra using the atomic multiplet cluster approach.

Figure 1

(Color) (a) Orbital-projected partial density of states of fivefold $\text{Mn}3d$ states on the Mn(4) site for an $A$-type antiferromagnetic structure of orthorhombic ${\text{DyMnO}}_3$ calculated with the $\text{GGA}+U$ method. The parameters in these calculations are described in the text. For each panel the upper half denotes the and the lower half the minority-spin states. The energy zero is at the Fermi energy $\left(E_f\right)$. (b) Electronic valence charge-density contour plot on the basal plane of ${\text{DyMnO}}_3$.The green and red balls denote Mn and O ions, respectively. Gray lobes on Mn ions indicate occupied $e_g^1\uparrow$.

Figure 2

(Color) (a) Experimental and (b) theoretical polarization-dependent $\text{Mn}{L}_{2,3}$-edge absorption spectra of single-crystalline ${\text{DyMnO}}_3$ for (a) $E\parallel a$ (red line), $E\parallel b$ (black line), and $E\parallel c$ (blue line). Experimental (green line) and theoretical (magenta line) LD spectra for $\left(E\parallel c\right)-\left(E\parallel a\right)$, $\left(E\parallel b\right)-\left(E\parallel c\right)$, and $\left(E\parallel b\right)-\left(E\parallel a\right)$ are shown in (c), (d), and (e), respectively.