Spin State of Negative Charge-Transfer Material ${\mathrm{SrCoO}}_3$

We employ the combination of the density functional theory and the dynamical mean-field theory to investigate the electronic structure and magnetic properties of ${\mathrm{SrCoO}}_3$, monocrystals of which were prepared recently. Our calculations lead to a ferromagnetic metal in agreement with experiment. We find that, contrary to some suggestions, the local moment in ${\mathrm{SrCoO}}_3$ does not arise from intermediate spin state, but is a result of coherent superposition of many different atomic states. We discuss how the attribution of magnetic response to different atomic states in solids with local moments can be quantified.

Figure 1

The spectral density per orbital: Co $d\mathrm{\text{−}}{e}_g$ (black, dark), Co $d\mathrm{\text{−}}{t}_{2g}$ (red, light), O $p_{\sigma }$ (darker blue, shaded), $p_{\pi }$ (lighter blue, shaded) in the PM DMFT (upper left), in LDA (lower left), and in FM DMFT (right panel) solution. The minority spin in the FM phase is distinguished by the minus sign.

Figure 2

The $k$-resolved spectral function $A_{\mathbf{k}}(\omega )$ along the high symmetry directions presented as a color plot of $A_{\mathbf{k}}(\omega )/[2+A_{\mathbf{k}}(\omega )]$. The PM solution is compared to the LDA bands (dots) in the upper left and in detail in the lower left panel. The same spectral function in the FM phase resolved into the majority (upper right) and minority (lower right) spin channels. The LSDA bands are marked with dots.

Figure 3

The imaginary part of the self-energy at $T=1160\mathrm{K}$ obtained with density–density interaction in the (a) PM and (b) FM phases. The diagonal ${\Sigma }_{ee}$ (black, dark) and ${\Sigma }_{tt}$ (red, light) are shown (for the FM phase only the majority $e_g$ and minority $t_{2g}$). The insets show the same functions on the imaginary axes together with the values on the Matsubara contour (open symbols). The zero frequency values are highlighted with the crosses. In panels (c) and (d) the real and imaginary parts of the self-energy obtained in the PM phase with the density–density (open circles) and with the SU(2) symmetric (filled squares) interaction at $T=232\mathrm{K}$ are compared.

Figure 4

(a) Weights of the dominant density–density multiplets of the Co $d$ shell at $T=232\mathrm{K}$. The inset shows the total weights of the different charge sectors ($d^5,d^6,\dots$), distinguished by shading in the main panel. (b) Comparison of the weights of different charge and spin sectors obtained with density–density (red, right column) and SU(2) symmetric (blue, left column) interactions. (c) Local spin–spin correlation in the PM phase with the density–density interaction. The inset shows the temperature dependence of the ordered (FM) Co moment.

Figure 5

The atomic state correlation matrix ${\Pi }_{AB}$ between the multiplets shown in Fig. 4 obtained with density–density interaction at 232 K. Upper left triangle shows the state-by-state relative contributions. The lower right triangle shows the contribution of multiplet pairs to the local susceptibility.