Iron-Based Low-Dimensional Magnets

Iron cations Fe$^{3+}$ (S = 5/2) in inorganic compounds usually effectively interact with each other along three directions, which excludes the presence of correlation effects associated with shortrange order. However, some systems with distant fragments containing Fe$^{3+}$ ions due to ligands or other nonmagnetic cations, retain signs of low-dimensional magnetic behavior both above and below the temperature of magnetic ordering. In this review, we have selected examples of iron compounds that can be attributed to the different classes of low-dimensional magnets, including magnetic clusters: dimers in Fe(Te$_{1.5}$Se$_{0.5}$)O$_5$Cl, magnetic chains in Bi$_2$Fe(SeO$_3$)$_2$OCl$_3$, Fe$_2$O(SeO$_3$)$_2$, magnetic chains with different spins Na$_x$Fe$_7$(PO$_4$)$_6$ (\textit{x} = 0, 0.65), MCuFe$_2$(VO$_4$)$_3$ (M = Li, Na), magnetic two-dimensional planes with triangular arrangement of magnetic ions MFeO$_2$ (M = Ag$^+$, Cu$^+$), MFe(MoO$_4$)$_2$ (M = K$^+$, Rb$^+$, Cs$^+$, Tl$^+$), NaFe$_3$(HPO$_3$)$_2$((H,F)PO$_2$OH)$_6$.