Spin correlations in the S = 1 armchair chain Ni2NbBO6 as seen from NMR* *Project supported by the National Key Research and Development Program of China (Grant No. 2016YFA0401802), the National Natural Science Foundation of China (Grant Nos. 11874057, 11504377, 11574288, 11874158, U1732273, and 21927814), and the Users with Excellence Program of Hefei Science Center CAS (Grant No. 2019HSC-UE008). A

Abstract

We report our nuclear magnetic resonance (NMR) study on the structurally spin chain compound Ni2NbBO6 with complex magnetic coupling. The antiferromagnetic transition is monitored by the line splitting resulting from the staggered internal hyperfine field. The magnetic coupling configuration proposed by the first-principle density functional theory (DFT) is supported by NMR spectral analysis. For the spin dynamics, a prominent peak at T ∼ 35 K well above the N éel temperature (T N ∼ 20 K at μ 0 H = 10 T) is observed from the spin-lattice relaxation data. As compared with the dc-susceptibility, this behavior indicates an antiferromagnetic coupling with the typical energy scale of ∼3 meV. Thus, the Ni2NbBO6 compound can be viewed as strongly ferromagnetically coupled armchair spin chains along the crystalline b-axis. These facts place strong constraints on the theoretical model for this compound.