Electronic structure and magnetism of KMF3(M=Mn,Fe,Co,Ni)

Antiferromagnetic electronic-structure calculations of the perovskite fluorides KM${\mathrm{F}}_3$ (M=Mn,Fe,Co,Ni) carried out using the linear muffin-tin orbital method are reported here. The calculations have successfully predicted the insulating gaps of the systems ${\mathrm{KMnF}}_3$ and ${\mathrm{KNiF}}_3$. However, in the cases of ${\mathrm{KFeF}}_3$ and ${\mathrm{KCoF}}_3$ the insulating gap could not be accounted for by these calculations and this is found to be due to the fact that the spin-density-functional theory is inadequate to show the splitting of the M ${\mathit{t}}_{2\mathit{g}}$ bands. However, the magnetic moments obtained from the calculations are comparable to the experimental values, and also the calculated density of states show good agreement overall with the photoemission data.