Crystal growth and magnetic ordering of Na₂Ni₂TeO₆ with honeycomb layers and Na₂Cu₂TeO₆ with Cu spin dimers

Abstract

We report on the crystal growth and magnetic property studies of layered Na2Ni2TeO6 and Na2Cu2TeO6. The former has a honeycomb layer composed of NiO6 octahedra and the latter is composed of paired CuO4 plaquettes connected through TeO6 octahedra.

Spin Correlations and Short‐Range Magnetic Order in the Honeycomb‐Layered Na2Ni2TeO6

“…For classical antiferromagnets, a sharp maximum on the magnetic susceptibility curve at the Neel temperature T N is usually observed. In our case, the broadened peak indicates the presence of the strong spin correlations above the phase transition and the overextending of magnetic order formation . As an example, a resembling situation was previously observed for a number of compounds, in particular for BaNi 2 V 2 O 8 , which also has a honeycomb arrangement of the magnetic layers .…”

“…Macromagnetic measurements showed the presence of a second‐order phase transition at low temperatures in Na 2 Ni 2 TeO 6 , associated with a transition from the paramagnetic to the magnetically ordered state . There is a broad peak on the magnetic susceptibility curve near 27 K, related to the antiferromagnetic (AFM) phase transition.…”

Sodium layer chiral distribution and spin structure of Na2Ni2TeO6 with a Ni honeycomb lattice

“…33 It is noted that the definition of a Ni S=1 spin chain in the 2D honeycomb network is ambiguous when three equivalent zigzag chains can be defined along the (1 0 0), (0 1 0) and (1 1 0) directions of a hexagonal system. According to the experimental and theoretical informations collected to date, including the identification of the AFM peak ( 1 2 0 1), the confirmed 3D AFM spin ordering, the spin anisotropy along the c-direction, 14 and the theoretically calculated ground state configurations [ Fig. 6(b)-(e)] of dominant next nearest neighbor AFM coupling J 2 with weak nearest neighbor FM coupling J 1 , a commensurate AFM spin structure is proposed and shown in Fig.…”

“…Judging from the χ c (T<T N ) drop to indicate the on-site spin anisotropy along the c-direction, 14 we have considered four possible magnetic configurations of the ground state to evaluate the three spin exchange parameters based on the first-principle density functional theory with a generalized gradient approximation (GGA), 16 including an antiferromagnetically coupled FM zigzag chain structure (AF1), a q=0 spin configuration for each honeycomb subnetwork (AF2), an A-type AFM spin structure similar to that found in Na 0.82 CoO 2 (AF3), 31 and a FM spin structure were calculated, as illustrated in Fig. 6 (b)-(e).…”

“…X-ray diffraction studies have shown that the crystal structure of Na 2 Ni 2 TeO 6 can be indexed with a space group P 6 3 /mcm satisfactorily, and a 3D antiferromagnetic (AFM) spin ordering of T N ∼27 K has been proposed; however, the impact of Na ion diffusion on the crystal and spin structure has never been explored in detail, in contrast to its sister compound Na x CoO 2 which has been studied extensively and shown rich physical insights. [3][4][5][6][7][8][9]12,14 It is highly desirable to investigate the 2D structure of the Na-layer that reflects the potential field generated by the (Te/Ni)-O honeycomb sublattice and its relationship to the magnetic structure of Ni spins. In particular, due to the diffusive nature of intercalated Na ions, a unique dynamic magneto-phonon coupling of the system could be revealed through the detailed analysis of the Na ion distribution and crystal structure change as a function of temperature.…”