Synthesis, structural, resonant and magnetic properties NaMnFe$_2$(VO$_4$)$_3$

The compound NaMnFe$_2$(VO$_4$)$_3$ was obtained by solid-phase synthesis from the starting oxides Na$_2$CO$_3$, Fe$_2$O$_3$, MnCO$_3$ and V$_2$O$_5$. The structural and static magnetic properties were studied, and the material was characterized using Mössbauer spectroscopy and electron paramagnetic resonance.
The parameters of the trigonal unit cell (space group $P$1) were determined and the crystal structure was refined (the coordinates of the atoms and their isotropic thermal parameters, the main lengths of interatomic bonds are given). The structural features of NaMnFe$_2$(VO$_4$)$_3$ allow for the existence of competing magnetic exchange interactions, as well as the formation of a state of local violation of charge neutrality.
The chain magnetic subsystem NaMnFe$_2$(VO$_4$)$_3$, formed by Mn$^{2+}$ and iron Mn$^{3+}$ cations, in the temperature range $T >$ 50 K is characterized primarily by antiferromagnetic exchange interaction and the molar value of the effective magnetic moment $\mu_{\mathrm{eff}\mathrm(ex)}$ = 9.9 $\mu_\mathrm{B}$. At temperatures below 10.5 K, the temperature dependence of the magnetic moment depends on the thermal history of the sample.