Crystal growth and magnetic properties of the coupled alternating S =1 spin chain Sr2Ni(Se O3)3

The structural, magnetic, and thermodynamic properties of a quasi-one-dimensional (1D) S=1 alternating spin chain compound Sr2Ni(SeO3)3 are investigated by using synchrotron x-ray powder diffraction, magnetic susceptibility χ(H,T), and heat capacity CP(H,T) measurements together with density functional theory (DFT) calculations. The χ(H,T) and CP(H,T) data reveal long-range antiferromagnetic order at TN=3.4(3) K and short-range order at Tm≈7.8K. The short-range magnetic order together with 95% of spin entropy release above TN signifies the importance of 1D spin correlations persisting to ∼8TN. Theoretical DFT calculations with generalized gradient approximation determine leading exchange interactions, suggesting that interchain interactions are responsible for the observed long-range magnetic ordering. In addition, the temperature-field phase diagram of Sr2Ni(SeO3)3 is determined based on the χ(T,H) and CP(T,H) data. Interestingly, a nonmonotonic phase boundary of Tm is found for an external field applied along a hard axis. Our results suggest that the ground state and magnetic behavior of Sr2Ni(SeO3)3 rely on the interplay of single-ion anisotropy, bond alternation, and interchain interactions.