Structural and magnetic characterization of the elusive Jahn-Teller active NaCrF3

We report on the structural and magnetic properties of the elusive Jahn-Teller active compound ${\mathrm{NaCrF}}_{3}$, for first time synthesized in large quantities allowing detailed characterization. The crystal structure of ${\mathrm{NaCrF}}_{3}$ is initially described from a DFT model, which helped serve as the basis for indexing and structure determination confirmed by high-resolution synchrotron x-ray diffraction experiments. ${\mathrm{NaCrF}}_{3}$ adopts the triclinic space group $P\overline{1}$ (isostructural with ${\mathrm{NaCuF}}_{3}$). Magnetometry studies at low temperature show that ${\mathrm{NaCrF}}_{3}$ is a weak antiferromagnet, Weiss temperature $\ensuremath{\theta}=\ensuremath{-}4$ K. The N\'eel temperature is ${T}_{N}=21.3$ K and the paramagnetic moment $\ensuremath{\mu}=4.47\phantom{\rule{0.28em}{0ex}}{\ensuremath{\mu}}_{{}_{B}}$ is in accordance with the theoretical $S=2$. Field-dependent measurements between 2 and 12 K unveil the onset of metamagnetic behavior. Our experiments revealed a weakly canted $A$-type magnetic structure observed by neutron powder diffraction, with a magnetic propagation vector $(1/2,1/2,0)$ and a magnetic moment of $3.51\phantom{\rule{4pt}{0ex}}{\ensuremath{\mu}}_{B}$ at 1.5 K. Our results shed further light on the Jahn-Teller effects and strong correlations as a function of $A$-ion size in the family $A{\mathrm{CrF}}_{3}$.