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Instruments / Technical Area	Publication Details	Published
I11-High Resolution Powder Diffraction	Magnetic structure and exchange interactions in the Heisenberg pyrochlore antiferromagnet Gd2Pt2O7 Philip G. Welch , Joseph A. M. Paddison , Manh Duc Le , Jason S. Gardner , Wei-Tin Chen , Andrew R. Wildes , Andrew L. Goodwin , J. Ross Stewart Physical Review B 105 DOI: 10.1103/PhysRevB.105.094402 Show Abstract ▼ Abstract: The Heisenberg pyrochlore antiferromagnet Gd 2 Pt 2 O 7 is one of a series of gadolinium pyrochlore compounds with a variety of B-site cations. Despite the expected simplicity of a spin-only Gd 3 + Heisenberg interaction model, the gadolinium pyrochlore series exhibits various complex magnetic ground states at low temperature. Gd 2 Pt 2 O 7 displays the highest temperature magnetic order of the series with T N = 1.6 K, which has been attributed to enhanced superexchange pathways facilitated by empty 5 d e g Pt orbitals. In this study, we use various neutron scattering techniques on an isotopically enriched polycrystalline 160 Gd 2 Pt 2 O 7 sample to examine the magnetic structure and spin-wave excitation spectrum below T N in order to extract the dominant exchange interactions. We find that the ground-state magnetic structure is the Palmer-Chalker state previously seen in Gd 2 Sn 2 O 7 with an associated gapped excitation spectrum consistent with enhanced exchange interactions between further near-neighbor Gd 3 + ions. We confirm this exchange model with analysis of the magnetic diffuse scattering in the paramagnetic regime using polarized neutrons.	Mar 2022
I11-High Resolution Powder Diffraction	Sample dependence of magnetism in the next-generation cathode material LiNi0.8Nn0.1Co0.1O2 Paromita Mukherjee , Joseph A. M. Paddison , Chao Xu , Zachary Ruff , Andrew R. Wildes , David A. Keen , Ronald I. Smith , Clare P. Grey , Sian E. Dutton Inorganic Chemistry DOI: 10.1021/acs.inorgchem.0c02899 Diamond Proposal Number(s): [25186] Show Abstract ▼ Abstract: We present a structural and magnetic study of two batches of polycrystalline LiNi0.8Mn0.1Co0.1O2 (commonly known as Li NMC 811), a Ni-rich Li ion battery cathode material, using elemental analysis, X-ray and neutron diffraction, magnetometry, and polarized neutron scattering measurements. We find that the samples, labeled S1 and S2, have the composition Li1–xNi0.9+x–yMnyCo0.1O2, with x = 0.025(2), y = 0.120(2) for S1 and x = 0.002(2), y = 0.094(2) for S2, corresponding to different concentrations of magnetic ions and excess Ni2+ in the Li+ layers. Both samples show a peak in the zero-field-cooled (ZFC) dc susceptibility at 8.0(2) K, but the temperature at which the ZFC and FC (field-cooled) curves deviate is substantially different: 64(2) K for S1 and 122(2) K for S2. The ac susceptibility measurements show that the transition for S1 shifts with frequency whereas no such shift is observed for S2 within the resolution of our measurements. Our results demonstrate the sample dependence of magnetic properties in Li NMC 811, consistent with previous reports on the parent material LiNiO2. We further establish that a combination of experimental techniques is necessary to accurately determine the chemical composition of next-generation battery materials with multiple cations.	Dec 2020
I15-Extreme Conditions	Encoding complexity within supramolecular analogues of frustrated magnets Andrew Cairns , Matthew Cliffe , Joseph Paddison , Dominik Daisenberger , Matthew G. Tucker , François-Xavier Coudert , Andrew L. Goodwin Nature Chemistry 8, 442 - 447 DOI: 10.1038/nchem.2462 Show Abstract ▼ Abstract: The solid phases of gold(I) and/or silver(I) cyanides are supramolecular assemblies of inorganic polymer chains in which the key structural degrees of freedom—namely, the relative vertical shifts of neighbouring chains—are mathematically equivalent to the phase angles of rotating planar (‘XY’) spins. Here, we show how the supramolecular interactions between chains can be tuned to mimic different magnetic interactions. In this way, the structures of gold(I) and/or silver(I) cyanides reflect the phase behaviour of triangular XY magnets. Complex magnetic states predicted for this family of magnets—including collective spin-vortices of relevance to data storage applications—are realized in the structural chemistry of these cyanide polymers. Our results demonstrate how chemically simple inorganic materials can behave as structural analogues of otherwise inaccessible ‘toy’ spin models and also how the theoretical understanding of those models allows control over collective (‘emergent’) phenomena in supramolecular systems.	May 2016

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