Abstract
Materials composed of spin-1 antiferromagnetic (AFM) chains are known to adopt complex ground states that are sensitive to the single-ion-anisotropy (SIA) energy (D), and intrachain (J0) and interchain (J1,2′) exchange energy scales. While theoretical and experimental studies have extended this model to include various other energy scales, the effect of the lack of a common SIA axis is not well explored. Here we investigate the magnetic properties of Ni(pyrimidine)(H2O)2(NO3)2, a chain compound where the tilting of Ni octahedra leads to a twofold alternation of the easy-axis directions along the chain. Muon-spin relaxation measurements indicate a transition to long-range order at TN=2.3K and the magnetic structure is initially determined to be antiferromagnetic and collinear using elastic neutron diffraction experiments. Inelastic neutron scattering measurements were used to find J0=5.107(7)K, D=2.79(1)K,J1′=0.00(5)K, J2′=0.18(3)K, and a rhombic anisotropy energy E=0.19(9)K. Mean-field modeling reveals that the ground state structure hosts spin canting of φ≈6.5∘, which is not detectable above the noise floor of the elastic neutron diffraction data. Monte Carlo simulation of the powder-averaged magnetization, M(H), is then used to confirm these Hamiltonian parameters, while single-crystal M(H) simulations provide insight into features observed in the data.
| Original language | English |
|---|---|
| Article number | 014421 |
| Journal | Physical Review B |
| Volume | 111 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 1 2025 |
Funding
We are indebted to the late Jamie Manson for instigating this work, for his role in designing and growing the samples and for many other invaluable contributions. We thank T. Orton and P. Ruddy for their technical assistance. We also thank R. Coldea, D. M. Pajerowski, C. Stock, and J. A. Villa for valuable discussions and B. M. Huddart for his assistance with the muon measurements. S.V. thanks the UK Engineering and Physical Sciences Research Council (EPSRC) for supporting his studentship. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 681260) and EPSRC (Grant No. EP/N024028/1). A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreements No. DMR-1644779 and No. DMR-2128556, the US Department of Energy (DoE) and the State of Florida. J.S. acknowledges support from the DoE BES FWP “Science of 100 T”. S.J.B. was funded by UK Research and Innovation (UKRI) under the UK government's Horizon Europe funding guarantee (Grant No. EP/X025861/1). The authors also thank National Science Foundation (NSF) for funding (NSF CHE-1827313). Part of this work was carried out at the Swiss Muon Source, Paul Scherrer Institut and we are grateful for the provision of beamtime (at the Dolly spectrometer).