Crystal Growth of Quantum Magnets in the Rare-Earth Pyrosilicate Family R2Si2O7 (R = Yb, Er) Using the Optical Floating Zone Method

Harikrishnan Nair,Tim Reeder,Tim Delazzer,Gavin Hester,Antony Sikorski,Kate Ross

doi:10.3390/cryst9040196

Harikrishnan Nair, Tim Reeder + Show 4 more

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https://doi.org/10.3390/cryst9040196

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Abstract

We report on the crystal growth of rare-earth pyrosilicates, R 2Si 2O 7 for R = Yb and Er using the optical floating zone method. The grown crystals comprise members from the family of pyrosilicates where the rare-earth atoms form a distorted honeycomb lattice. C-Yb 2Si 2O 7 is a quantum dimer magnet with field-induced long range magnetic order, while D-Er 2Si 2O 7 is an Ising-type antiferromagnet. Both growths resulted in multi-crystal boules, with cracks forming between the different crystal orientations. The Yb 2Si 2O 7 crystals form the C-type rare-earth pyrosilicate structure with space group C 2 / m and are colorless and transparent or milky white, whereas the Er-variant is D-type, P 2 1 / b , and has a pink hue originating from Er 3 +. The crystal structures of the grown single crystals were confirmed through a Rietveld analysis of the powder X-ray diffraction patterns from pulverized crystals. The specific heat of both C-Yb 2Si 2O 7 and D-Er 2Si 2O 7 measured down to 50 mK indicated a phase transition at T N ≈ 1.8 K for D-Er 2Si 2O 7 and a broad Schottky-type feature with a sharp anomaly at 250 mK in an applied magnetic field of 0.8T along the c-axis in the case of C-Yb 2Si 2O 7 .

Highlights

The rare-earth pyrosilicates, R2 Si2 O7 where R is a rare-earth element, were studied in the past owing to the polymorphism that these compounds displayed as a function of temperature and the ionic size of the rare-earth R3+ [1]
Single crystals and ceramics of Er2 Si2 O7 were studied in detail using X-ray investigations to clearly document the phase transitions between different structure types (P1 → C2/m → P21 /b) as a function of synthesis temperature [7,9]
During the powder synthesis of Yb2 Si2 O7 and Er2 Si2 O7, we found that (Yb/Er)2 SiO5 was a common sample impurity, which was found to be more prominent in X-ray powder diffraction of the surface material compared to the bulk

Summary

Introduction

The rare-earth pyrosilicates, R2 Si2 O7 where R is a rare-earth element, were studied in the past owing to the polymorphism that these compounds displayed as a function of temperature and the ionic size of the rare-earth R3+ [1]. Though single crystals of several rare-earth pyrosilicates, R2 Si2 O7 (R = Tm, Er, Ho, Dy), have been prepared via flux growth [6,7], detailed studies on the magnetism of the rare-earth lattice forming a distorted honeycomb structure in these compounds are lacking and, in particular, the crystals prepared by flux method are not large enough for neutron scattering investigations. Single crystals and ceramics of Er2 Si2 O7 were studied in detail using X-ray investigations to clearly document the phase transitions between different structure types (P1 → C2/m → P21 /b) as a function of synthesis temperature [7,9]. The crystals obtained by this method are suitable for single crystal neutron scattering investigations, the first of which have recently been carried out by our group [13]

Crystal Growth Using Optical Floating Zone Method

Method

Powder X-ray Diffraction and Laue

Specific Heat of C-Yb2 Si2 O7 and D-Er2 Si2 O7

Findings

Conclusions