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

Abstract

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) Å, b = 3.9300(4), c = 14.3827(14), 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 Mössbauer 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 [EuSe₂Se_2/2Se_4/4] layers, yielding a magnetic substructure with Eu-Eu distances of ~3.93 Å and a longer ~4.91 Å. 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 T_N1 ~ 8K, with glassy character, and at T_N2 ~ 4 K implying a complex canted antiferromagnetic or ferrimagnetic ground state.