Magnetic order induced by magnetic impurities in the Haldane chain compound SrNi2V2O8

Understanding the topological properties of Haldane spin systems offers promising avenues for exploring exotic quantum phases. We investigate the impact of S = 5/2 Mn ²⁺ impurities on the magnetic properties of SrNi ₂V ₂O ₈, a well-known Haldane spin gapped system. Structural characterizations of SrNi _{2- x}Mn _xV ₂O ₈ ( x = 0.05, 0.15, 0.30 and 0.60) through Rietveld analyses of X-ray diffraction data confirm the preservation of the I4 ₁ cd space group for all studied x , along with a preferential insertion of Mn ²⁺ ions into Ni ²⁺ sites. Magnetic susceptibility and magnetization data unveil a magnetic transition occurring in the temperature range of T = 93–99.3 K for x = 0.05–0.60. Dielectric data evince the absence of coupling between magnetic and ferroelectric phases. Notably, the magnetic ordering temperature varies little over a wide range of Mn concentrations, while notable anomalies are observed at x = 0.15. This peculiar behavior suggests that, across low-to-high concentrations, disorder-induced magnetic moments compete with the formation of spin singlets between the nearest Mn ²⁺ impurities, which cancel out the magnetic moments.