Electronic structure of ${\text{Sr}}_{0.8-y}{\text{La}}_{0.2+y}{\text{Ti}}_{0.8}{\text{Cr}}_{0.2}{\text{O}}_3$ studied by photoemission spectroscopy and first-principles band structure calculations

We have investigated electron-doping effects on the electronic structure of ${\text{Sr}}_{0.8-y}{\text{La}}_{0.2+y}{\text{Ti}}_{0.8}{\text{Cr}}_{0.2}{\text{O}}_3$ using high-resolution photoemission spectroscopy and first-principles band structure calculations. Photoemission results showed that the $\text{Cr}3d$ peak intensity is independent of the carrier concentration $\left(y\right)$, while the spectral weight near the Fermi level, composed of the $\text{Ti}3d$ states, is proportional to $y$ at a fixed spin concentration. Detailed comparisons between the photoemission spectra and the band structure calculations including magnetic-moment calculations reveal that the large energy separation between the $\text{Cr}3d$ states and the $\text{Ti}3d$ states plays an important role to control the electric and magnetic properties in this system.

Figure 1

(Color online). (a) $y$ dependence of valence-band photoemission spectra from ${\text{Sr}}_{0.8-y}{\text{La}}_{0.2+y}{\text{Ti}}_{0.8}{\text{Cr}}_{0.2}{\text{O}}_3$ taken with 150 eV at 50 K. [(b) and (c)] Integrated intensity of the features $B$ and $A$ as a function of $y$, respectively. Those intensity is normalized by the averaged intensity of $B$ for feature $B$ and by the intensity at (0.1, 0.1) for feature $A$. Each integration windows are represented by dotted rectangles in (a), which are also given in the text.

Figure 2

(Color). (a) Total and partial densities of states of ${\text{Sr}}_{1-\left(x+y\right)}{\text{La}}_{x+y}{\text{Ti}}_{1-x}{\text{Cr}}_x{\text{O}}_3$ for $\left(x,y\right)=\left(0.2,0.2\right)$ calculated with the KKR-CPA-LDA method. The cubic unit cell is chosen. (b) Valence-band photoemission spectra of (0.2, 0.2) taken with 150 eV at 50 K together with the theoretical curve. (c) Schematic electronic structure of SLTCO in (c1) and (c3), LSTO in (c2), and LCO in (c4) (Ref. 15). In (c3), we align the schematic calculated DOS to the experimental $\text{O}2p$ position.

Figure 3

(Color). [(a) and (b)] Near-$E_{\text{F}}$ spectra compared with the band theory for (0.2, 0.2) and (0.2, 0.1), respectively. The theoretical curves which were multiplied by the same constant number with Fig. 2b. [(c) and (d)] Symmetrized experimental and theoretical spectra of (0.2, 0.2) and (0.2, 0.1), respectively. Zero lines are indicated by the dotted horizontal lines. Note that both experimental and theoretical spectra of (0.2, 0.2) are offset.

Figure 4

(Color online). (a) Peak intensity of the $\text{Cr}3d$ states (theory: feature $\beta$, experiment: feature $B$). (b) Peak intensity of the near-$E_{\text{F}}$ states (theory: feature $\alpha$, experiment: feature $A$). [Note that the experimental lines are the same as Figs. 1b, 1c.] The intensity normalization of the theoretical lines is the same as in Figs. 1b, 1c. The integration windows are given in Ref. 26.

Figure 5

(Color online). Calculated magnetic moment ($M$: numbers in ovals) of ${\text{Sr}}_{1-\left(x+y\right)}{\text{La}}_{x+y}{\text{Ti}}_{1-x}{\text{Cr}}_x{\text{O}}_3$ as a function of $x$ and $y$ (in ${\mu }_B$) (Ref. 29).