Synthesis, Crystal Structure, and Physical Properties of the Eu(II)-Based Selenide Semiconductor: EuHfSe3

Black needle-shaped crystals of a novel Eu(II)-containing chalcogenide semiconductor, EuHfSe3, have been synthesized at high temperatures using sealed-tube solid-state reaction techniques. Single crystal X-ray diffraction data (XRD) was used to characterize its structure as forming in the orthorhombic space group Pnma (a = 8.887(1) A, b = 3.9300(4) A, c = 14.3827(14) A, and Z = 4) with the NH4CdCl3 structure type. The extended structure is comprised of [HfSe3]2- chains which are charge balanced by Eu(II) cations. 151Eu Mossbauer spectroscopic measurements were consistent with the coordination of only Eu(II) cations in bicapped trigonal prisms of EuSe8. The latter polyhedra are condensed via face-sharing into corrugated [EuSe2Se2/2Se4/4] layers, yielding a magnetic substructure with Eu-Eu distances of ~3.93 A and a longer ~4.91 A. This structural feature of the NH4CdCl3-type structure has been probed for its impact on the magnetic and thermodynamic properties. Magnetic susceptibility and heat capacity measurements uncover two magnetic transitions at TN1 ~ 8 K, with glassy character, and at TN1 ~ 4 K implying a complex canted antiferromagnetic or ferrimagnetic ground state.