Magnetic properties of a staggered $S=1$ chain with an alternating single-ion anisotropy direction

Journal Article · 16 January 2025 · Physical Review. B

DOI: https://doi.org/10.1103/PhysRevB.111.014421 · OSTI ID:2555929

Vaidya, S. ; Curley, S. P. M. ; Manuel, P. ; Stewart, J. Ross ; Le, M. Duc ; Balz, C.; Shiroka, T.; Blundell, S. J. ; Wheeler, K. A. ; Calderon-Lin, I.; Manson, Z. E.; Manson, J. L.; Singleton, J.; Lancaster, T. ; Johnson, R. D. ; Goddard, P. A.

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 ( $J_0$ ) and interchain ( $J_{1,2}^{\prime }$ ) 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 $\mathrm{Ni}\left(\mathrm{pyrimidine}\right){\left({\mathrm{H}}_2\mathrm{O}\right)}_2{\left({\mathrm{NO}}_3\right)}_2$ , 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 $T_{\text{N}}=2.3\mathrm{K}$ 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 $J_0=5.107\left(7\right)\mathrm{K}, D=2.79\left(1\right)\mathrm{K},J_1^{\prime }=0.00\left(5\right)\mathrm{K}, J_2^{\prime }=0.18\left(3\right)\mathrm{K}$ , and a rhombic anisotropy energy $E=0.19\left(9\right)\mathrm{K}$ . Mean-field modeling reveals that the ground state structure hosts spin canting of $\varphi \approx 6.5^{\circ }$ , which is not detectable above the noise floor of the elastic neutron diffraction data. Monte Carlo simulation of the powder-averaged magnetization, $M\left(H\right)$ , is then used to confirm these Hamiltonian parameters, while single-crystal $M\left(H\right)$ simulations provide insight into features observed in the data. Published by the American Physical Society 2025

• Sponsoring Organization: USDOE
• OSTI ID: 2555929
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 1 Vol. 111; ISSN 2469-9950; ISSN PRBMDO
• Publisher: American Physical SocietyCopyright Statement
• Country of Publication: United States
• Language: English