Magnetic properties of the quasi-one-dimensional $S=1$ spin chain antiferromagnet $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$

We report a quasi-one-dimensional $S=1$ spin chain compound $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$. This magnetic system has been investigated by magnetic susceptibility, specific heat, and neutron powder diffraction. These results indicate that $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$ develops a short-range magnetic correlation around $T\sim 22\mathrm{K}$. With further cooling, an antiferromagnetic phase transition is observed at $T_{\mathrm{N}}\sim 5.4\mathrm{K}$. Neutron powder diffraction revealed antiferromagnetic noncollinear order with a commensurate propagation vector $\mathbf{k}=\left(1/2,1,0\right)$. The refined magnetic moment size of ${\mathrm{Ni}}^{2+}$ at 1.5 K is $1.84{\mu }_{\mathrm{B}}$, and its noncollinear spin texture is confirmed by first-principles calculations. Inelastic neutron-scattering results and density functional theory calculations confirmed the quasi-one-dimensional nature of the spin systems.

Figure 1

(a) The crystal structure of $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$. (b) Rietveld refined powder XRD spectrum of $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$ at room temperature.

Figure 2

(a) Temperature-dependent magnetic susceptibility χ($T$) of $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$ measured under ${\mu }_{0}H=0.1\mathrm{T}$ (red). The inverse magnetic susceptibility and corresponding linear Curie-Weiss fit (blue). (b) χ($T$) measured under various magnetic fields and the inset displays the derivative dχ($T$)/$\mathit{dT}$ around 5 K. (c) Magnetic field-dependent magnetization $M\left({\mu }_{0}H\right)$ of $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$ measured at $T=2$, 5, 10, and 100 K. (d) Temperature-dependent specific heat $C_{\mathrm{P}}\left(T\right)$ under zero and various magnetic fields.

Figure 3

(a) The NPD data of $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$ and its refinements collected at 20 K with the wavelength of $1.54\AA$. (b) shows the data measured at 1.5 K with the wavelength of $2.41\AA$. The vertical bars indicate the nuclear and magnetic Bragg peak positions, as well as the aluminum peaks from the sample holder. The inset in (b) shows a zoomed-in view of the low-$Q$ diffraction data that includes the magnetic peaks (1/2,1,0) and (1/2,0,1).

Figure 4

(a) Magnetic structure of $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$ determined by the neutron-diffraction refinement and verified by DFT calculation. $J_1, J_2$, and $J_3$ denote the nearest-, next-nearest-, and next-next-nearest-neighbor exchanges. (b) Inelastic neutron-scattering data obtained from $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$ powder at 1.7 K using the HYSPEC spectrometer. (c) Calculated powder averaged spin-wave excitation spectrum, $S$($Q, E$), using a spin Hamiltonian described in the text.

Figure 5

The density of states of $\mathrm{BaNi}{\mathrm{Te}}_2{\mathrm{O}}_7$. The SOC effect is almost negligible to the electronic structure. The hybridization between Ni's $3d$ orbitals and O's $2p$ orbitals contributes to the states around the Fermi level.