Static and resonant properties of decorated square kagome lattice compound KCu\(_7\)(TeO\(_4\))(SO\(_4\))\(_5\)Cl

• Published in: arXiv.org 2023-12
• Main Authors: Markina, M M, Berdonosov, P S, Vasilchikova, T M, Zakharov, K V, Murtazoev, A F, Dolgikh, V A, Moskin, A V, Glazkov, V N, Smirnov, A I, Vasiliev, A N
• Format: Article
• Language: English
• Subjects: Antiferroelectricity; Antiferromagnetism; Copper; Decoration; Electron paramagnetic resonance; Electron spin; Electrons; Excitation spectra; Interaction parameters; Kagome lattice; Low temperature; Magnetic fields; Magnetic permeability; Magnetic properties; Magnetism; Phase transitions; Physical properties; Spectrum analysis; Spin liquid; Spin resonance; Subsystems
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2212.11623

The magnetic subsystem of nabokoite, KCu\(_7\)(TeO\(_4\))(SO\(_4\))\(_5\)Cl, is constituted by copper ions forming a buckled square kagomé lattice decorated by quasi-isolated ions. This combination determines peculiar physical properties of this compound evidenced in electron spin resonance (ESR) spectroscopy, dielectric permittivity \(\varepsilon\), magnetization \(M\) and specific heat \(C_p\) measurements. At lowering temperature, the magnetic susceptibility \(\chi = M/H\) passes through a broad hump inherent for low-dimensional magnetic systems at about 150 K and a sharp peak at antiferromagnetic phase transition at \(T_N = 3.2 \)K. The \(C_p(T,H)\) curves demonstrate additional peak-like anomaly at \(T_{peak}= 5.7\)K robust to magnetic field. The latter can be ascribed to low-lying singlet excitations filling the singlet-triplet gap in magnetic excitation spectrum of the square kagomé lattice [J.Richter, O.Derzhko and J.Schnack, Phys. Rev. B \textbf{105} (2022) 144427]. ESR spectroscopy provides indications that antiferromagnetic structure below \(T_N\) is non-collinear. Separate issue is the observation of antiferroelectric-type behavior in \(\varepsilon\) at low temperatures, which tentatively reduces the symmetry and partially lifts frustration of magnetic interactions of decorating copper ions with buckled square kagomé lattice. These complex thermodynamic and resonant properties signal the presence of two weakly coupled magnetic subsystems in nabokoite, namely a spin-liquid in square kagomé lattice layers and an antiferromagnet represented by decorating ions.