A neutron diffraction demonstration of long-range magnetic order in the quasicrystal approximant DyCd6

D H Ryan,A I Goldman,A Kreyssig,J M Cadogan,P C Canfield,T Kong

doi:10.1063/1.5079991

Abstract

We have used neutron powder diffraction to demonstrate the existence of long-range antiferromagnetic order of Ising-like Dy moments in the DyCd6 quasicrystal approximant phase. This cubic compound undergoes a slight distortion to a monoclinic cell at low temperatures. The Néel temperature is 18.0(2) K and the magnetic order of the Dy sublattice may be described in the parent cubic Im3¯ structure using a combination of two propagation vectors, k1 = [0 0 0] and k2 = [12 0 12], yielding ‘anti-I’ order. Alternatively, when referred to the monoclinic C2/c cell, the magnetic structure may be described by a single propagation vector: k = [1 0 0].

Highlights

The cadmium-rich side of most rare-earth (R) cadmium alloy phase diagrams contains RCd6, a 1/1 cubic approximant based on a bcc packing of interpenetrating Tsai-type icosahedral clusters.1 These clusters are the building blocks of two remarkable families of thermodynamically stable binary quasicrystalline rare-earth containing phases: YbCd5.72 and RCd7.5 (R = Gd – Tm, Y)3 that lie either side of the cubic RCd6 phase
We have used neutron powder diffraction to demonstrate the existence of long-range antiferromagnetic order of Ising-like Dy moments in the DyCd6 quasicrystal approximant phase
The Néel temperature is 18.0(2) K and the magnetic order of the Dy sublattice may be described in the parent cubic Im3 structure using a combination of two propagation vectors, k1 = [0 0 0] and k2

Summary

Introduction

The cadmium-rich side of most rare-earth (R) cadmium alloy phase diagrams contains RCd6, a 1/1 cubic approximant based on a bcc packing of interpenetrating Tsai-type icosahedral clusters.. The cadmium-rich side of most rare-earth (R) cadmium alloy phase diagrams contains RCd6, a 1/1 cubic approximant based on a bcc packing of interpenetrating Tsai-type icosahedral clusters.1 These clusters are the building blocks of two remarkable families of thermodynamically stable binary quasicrystalline rare-earth containing phases: YbCd5.72 and RCd7.5 (R = Gd – Tm, Y) that lie either side of the cubic RCd6 phase. Together, these three systems provide an invaluable window onto the properties of quasicrystalline materials. The properties of the RCd6 compounds are quite complex, with most undergoing a structural change from cubic to monoclinic near 170 K5 and many exhibiting multiple features in heat capacity (Cp) and susceptibility (χ) at much lower temperatures that likely reflect magnetic ordering. the sharp nature of the features in Cp and χ1,5,6 have been interpreted as evidence for long-ranged magnetic order rather than the spin-glasslike behaviour observed in most other quasicrystalline systems.

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