Low‐temperature phase transition and magnetic properties of K3YbSi2O7. Issue 4 (27th July 2021)

• Record Type: Journal Article
• Authors: Dabić, Predrag; Kahlenberg, Volker; Krüger, Biljana; Rodić, Marko; Kovač, Sabina; Blanuša, Jovan; Jagličić, Zvonko; Karanović, Ljiljana; Petříček, Václav; Kremenović, Aleksandar
• Is Part Of: Acta crystallographica. Volume 77:Issue 4(2021)
• Page Start: 584
• Page End: 593
• Publication Date: 2021-07-27
• Subjects: alkali rare‐earth silicates -- phase transition -- magnetic properties -- crystal field splitting -- lanthanide silicates
• DOI: 10.1107/S2052520621006077
• Languages: English
• ISSNs: 2052-5206

Abstract

Abstract : A low‐temperature displacive‐type phase transition in K3 YbSi2 O7 occurring at ≃ 210 K is reported, where the symmetry of the ambient‐temperature polymorph decreases from hexagonal (space group P 63 /mmc ) to orthorhombic (space group Cmcm ). The structural relationships between the two polymorphs and their magnetic properties are described. Abstract : The new ambient‐temperature hexagonal (space group P 63 /mmc ) polymorph of tripotassium ytterbium(III) disilicate (β‐K3 YbSi2 O7 ) has been synthesized by the high‐temperature flux method and subsequently structurally characterized. In the course of the temperature‐dependent single‐crystal diffraction experiments, a phase transformation of β‐K3 YbSi2 O7 to a novel low‐temperature orthorhombic phase (β′‐K3 YbSi2 O7, space group Cmcm ) has been observed at about 210 K. β‐K3 YbSi2 O7 is isostructural with K3 ErSi2 O7, whereas β′‐K3 YbSi2 O7 adopts a new type of structure. Both compounds can be built up from a regular alternation of layers of two types, which are parallel to the (001) plane. In the octahedral layer, YbO6 octahedra are isolated and linked by K1O6+3 polyhedra. The second, slightly thicker sorosilicate layer is formed by a combination of Si2 O7 dimers and K2O6+3 polyhedra. The boundary between the layers is a pseudo‐kagome oxide sheet based on 3.6.3.6 meshes. The phase transition is due to a tilt of the two SiO4 tetrahedra forming a single dimer which induces a decrease of the Si—O—Si angle between bridging Si—O bonds from 180° (dictated by symmetry in space group P 63 / mmc ) to ≃164°. Magnetic characterization indicates that K3 YbSi2 O7 remains paramagnetic down to 2 K, showing no apparent influence of the phase transformation on its magnetic properties. Analysis of the magnetization data revealed the positions of the three lowest crystal field levels of the Yb 3+ cations, as well as the corresponding projections of their angular momentum on the direction of the magnetic field.