Synthesis and properties of the compound Na$_2$FeLiSi$_6$O$_{15}$

The structural, resonance, and static magnetic properties of the Na$_2$FeLiSi$_6$O$_{15}$ compound obtained by solid-phase synthesis from the initial oxides Li$_2$CO$_3$, Na$_2$CO$_3$, Fe$_2$O$_3$, SiO$_2$ were studied. It is shown that iron cations in emeleusite, which are in the high-spin state Fe$^{3+}$ ($S$ = 5/2, 3d$^5$) and in ideal octahedra constituted by oxygen anions, in the temperature range of 4.2 – 300 K form a paramagnetic subsystem with a molar value of the effective magnetic moment $\mu_{\mathrm{eff}}$ = 6.02 $\mu_{\mathrm{B}}$ and with a $g$-factor at $T$ = 297.8 K equal to 2.092. Apparently, due to the separation of iron cations by groups of non-magnetic ions SiO$_4$, LiO$_4$, the exchange interaction between them is small (the shortest distances Fe–Fe are equal to 5.867(3) $\mathring{\mathrm{A}}$), which leads to the absence of long-range magnetic order.