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The idea of controlling the magnetic ground state of a spin-1 one-dimensional
antiferromagnetic (1d AFM) quantum magnets has long been of interest to physicists. In the
study of anisotropic 1d AFM systems based on Ni 2+ compounds, a series of topologically
protected quantum phases was observed, one of these phases is the topologically protected
Haldane phase [1, 2]. The magnetic ground state of such a system is sensitive to the relative
magnitude of the single-ion anisotropy (D) and the intrachain (J) exchange interaction
parameters. The D/J ratio dictates the system’s placement in one of three competing phases: a
Haldane gapped phase, a quantum paramagnet, and an XY-ordered state, with a quantum critical
point at their junction at D/J = 1. We present the study of the crystal structure and magnetic
properties of compound [Ni(2aepy) 2 Cl (H 2 O)] ClH 2 O (2aepy = 2 – aminoethylpyridine).
Hexacoordinate Ni 2+ ions form a zig-zag chain based on hydrogen bonds and running along
crystallographic b-axis. The analysis of the experimental susceptibility using a model of spin-1
anisotropic AFM chain yielded parameter values D/k B = 4.05 K and J/k B = 3.55 K. A theoretical
prediction of D/k B = 3.7 K using ab initio approach is very close to our experimental value.
[1] F.D.M. Haldane, Phys. Lett. A 93, 464 (1983).
[2] F.D.M. Haldane, Phys. Rev. Lett. 50, 1153 (1983).
[3] J.L. Manson, et al., Inorg. Chem. 51, 7520 (2012).
[4] D.M. Pajerowski, et al., arXiv:2001.08555.
This work was supported by VEGA 1/0426/19, APVV-18-0197, and APVV-18-0016 projects.
