Hf₃Fe₄Sn₄ and Hf₉Fe_4-xSn_10+x: Two stannide intermetallics with low-dimensional iron sublattices

This article reports two new Hf-rich intermetallics synthesized using Sn flux: Hf₃Fe₄Sn₄ and Hf₉Fe_4-xSn_10+x. Hf₃Fe₄Sn₄ adopts an ordered variant the Hf₃Cu₈ structure type in orthorhombic space group Pnma with unit cell edges of a=8.1143(5) Å, b=8.8466(5) Å, and c=10.6069(6) Å. Hf₉Fe_4-xSn_10+x, on the other hand, adopts a new structure type in Cmc2₁ with unit cell edges of a=5.6458(3) Å, b=35.796(2) Å, and c=8.88725(9) Å for x=0. It exhibits a small amount of phase width in which Sn substitutes on one of the Fe sites. Both structures are fully three-dimensional and are characterized by pseudo one- and two-dimensional networks of Fe-Fe homoatomic bonding. Hf₉Fe_4-xSn_10+x exhibits antiferromagnetic order at T_N=46(2) K and its electrical transport behavior indicates that it is a normal metal with phonon-dictated resistivity. Hf₃Fe₄Sn₄ is also an antiferromagnet with a rather high ordering temperature of T_N=373(5) K. Single crystal resistivity measurements indicate that Hf₃Fe₄Sn₄ behaves as a Fermi liquid at low temperatures, indicating strong electron correlation.