Sc_{2}Ga_{2}CuO_{7}: A possible Quantum spin liquid near the percolation threshold

Abstract

Sc${}_2$Ga${}_2$CuO${}_7$ (SGCO) crystallizes in a hexagonal structure (space group: $P$$6$${}_3/mmc$),\textcolor{black}{{} which can be seen as an alternating stacking of single and double triangular layers. Combining neutron, x-ray, and resonant x-ray diffraction we establish that the single triangular layers are mainly populated by non-magnetic Ga${}^{3+}$ ions (85\% Ga and 15\% Cu), while the bi-layers have comparable population of Cu${}^{2+}$ and Ga${}^{3+}$} ions \textcolor{black}{(43\% Cu and 57\% Ga)}. Our susceptibility measurements in the temperature range 1.8 - 400 K give no indication of any spin-freezing or magnetic long-range order (LRO). We infer an effective paramagnetic moment ${\mu }_{eff}=1.79\pm 0.09$ ${\mu }_B$ and a Curie-Weiss temperature ${\theta }_{CW}$ of about $-44$ K, suggesting antiferromagnetic interactions between the Cu${}^{2+}$($S=1/2$) ions. Low-temperature neutron powder diffraction data showed no evidence for LRO down to 1.5 K. In our specific heat data as well, no anomalies were found down to 0.35 K, in the field range 0-140 kOe.\textcolor{black}{{} The magnetic specific heat, $C_m$, exhibits a broad maximum at around 2.5 K followed by a nearly power law $C$${}_m$$\propto$ $T$${}^{\alpha }$ behavior at lower temperatures, with $\alpha$ increasing from }0.3\textcolor{black}{{} to} 1.9\textcolor{black}{{} as a function of field for fields upto 90 kOe and then remaining at 1.9 for fields upto 140 kOe. Our results point to a disordered ground state in SGCO. }

10 pages, 13 figures

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• Ba${}_3$M${}_x$Ti${}_{3-x}$O${}_9$(M = Ir, Rh): A family of 5\textit{\textcolor{black}{d}}/4\textit{\textcolor{black}{d}}-based, diluted quantum spin liquids
• Signature of a randomness-driven spin-liquid state in a frustrated magnet
• Magnetic properties of triangular lattice antiferromagnets Ba3RB9O18 (R = Yb, Er)
• Quantum Spin Liquid State in the Disordered Triangular Lattice Sc2Ga2CuO7
• Electronic structure and magnetic properties of 3d-4f double perovskite material
• Spin liquid behavior of a three-dimensional magnetic system Ba${}_3$NiIr${}_2$O${}_9$ with $S$ = 1
• Dynamic magnetism in the disordered hexagonal double perovskite BaTi${}_{1/2}$Mn${}_{1/2}$O${}_3$