Evolution of structural and magnetic properties of Li₄Cu_1−xNi_xTeO₆ (x = 0, 0.1, 0.2, 0.5, and 1)

Li₄CuTeO₆ is a candidate material for quantum spin liquid (QSL) where the QSL state occurs primarily due to unavoidable anti-site disorder between Li⁺ and Cu²⁺ ions on triangular spin networks [1, 2]. We searched for nearby magnetic states and related compounds to elucidate the magnetic properties of Li₄MTeO₆ (M = Cu, Ni) system. Here, we present a comprehensive study of the structure and magnetic susceptibility of polycrystalline Li₄Cu_1-xNi_xTeO₆ (x ≈ 0, 0.1, 0.2, 0.5, and 1) samples. We compare our results with previous studies on Li₄CuTeO₆ (S=1/2) [1, 2] and Li₄NiTeO₆ (S=1) [3] compounds. The structure analysis reveals that full incorporation of Ni (x =1) at the Cu site leads to a contraction in unit cell volume by around 1% and confirms the stabilization of Li₄NiTeO₆ on a honeycomb spin network of Ni²⁺ ions. Magnetic susceptibility measurements do not show any indication of onset magnetic order down to 2 K in any sample. The magnetic susceptibility follows the Curie-Weiss law at high temperatures for all samples, with a drastic decrease in Weiss temperature θ_cw from -145 K to -6.15 K for x = 0 and 1, respectively. Our observations support the exotic quantum nature of the magnetic ground states in this series of compounds, Li₄Cu_1-xNi_xTeO_6.

[1] J. Khatua et al, Commun. Phys 5, 99 (2022).

[2] V. Kumar et al, Inorg. Chem. 51, 10471 - 10473 (2012).

[3] E. A. Zvereva et al, Jour. of Solid State Chemistry, 225, 89-96, (2015).