Large exchange anisotropy in quasi-one-dimensional spin- 12 fluoride antiferromagnets with a d(z2)1 ground state

Hybrid density functional calculations are performed for a variety of systems containing ${d}⁹$ ions $(\mathrm{C}{\mathrm{u}}²⁺$ and $\mathrm{A}{\mathrm{g}}²⁺)$ and exhibiting quasi-one-dimensional magnetic properties. In particular, we study fluorides containing these ions in a rarely encountered compressed octahedral coordination that forces the unpaired electron into the local $d({z}²)$ orbital. We predict that such systems should exhibit exchange anisotropies surpassing that of $\mathrm{S}{\mathrm{r}}₂\mathrm{Cu}{\mathrm{O}}₃$, one of the best realizations of a one-dimensional system known to date. In particular, we predict that the interchain coupling in the $\mathrm{A}{\mathrm{g}}²⁺$-containing $[\mathrm{AgF}][\mathrm{B}{\mathrm{F}}₄]$ system should be nearly four orders of magnitude smaller than the intrachain interaction. Our results indicate that quasi-one-dimensional spin-$\frac{1}{2}$ systems containing chains with spin sites in the $d{({z}²)}¹$ local ground state could constitute a versatile model for testing modern theories of quantum many-body physics in the solid state.