Crystal growth and magnetic properties of the coupled alternating S=1 spin chain Sr2Ni(SeO3)3

Abstract

The structural, magnetic, and thermodynamic properties of a quasi-one-dimensional (1D) $S=1$ alternating spin chain compound ${\mathrm{Sr}}_{2}\mathrm{Ni}{(\mathrm{Se}{\mathrm{O}}_{3})}_{3}$ are investigated by using synchrotron x-ray powder diffraction, magnetic susceptibility $\ensuremath{\chi}(H,T)$, and heat capacity ${C}_{\mathrm{P}}(H,T)$ measurements together with density functional theory (DFT) calculations. The $\ensuremath{\chi}(H,T)$ and ${C}_{\mathrm{P}}(H,T)$ data reveal long-range antiferromagnetic order at ${T}_{\mathrm{N}}=3.4(3)$ K and short-range order at ${T}_{\mathrm{m}}\ensuremath{\approx}7.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The short-range magnetic order together with 95% of spin entropy release above ${T}_{\mathrm{N}}$ signifies the importance of 1D spin correlations persisting to $\ensuremath{\sim}8{T}_{\mathrm{N}}$. 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 ${\mathrm{Sr}}_{2}\mathrm{Ni}{(\mathrm{Se}{\mathrm{O}}_{3})}_{3}$ is determined based on the $\ensuremath{\chi}(T,H)$ and ${C}_{\mathrm{P}}(T,H)$ data. Interestingly, a nonmonotonic phase boundary of ${T}_{\mathrm{m}}$ is found for an external field applied along a hard axis. Our results suggest that the ground state and magnetic behavior of ${\mathrm{Sr}}_{2}\mathrm{Ni}{(\mathrm{Se}{\mathrm{O}}_{3})}_{3}$ rely on the interplay of single-ion anisotropy, bond alternation, and interchain interactions.