Structural phase transitions in the kagome lattice based materials Cs2-xRbxSnCu3F12 (x = 0, 0.5, 1.0, 1.5)

The solid solution Cs2-xRbxSnCu3F12 (x = 0, 0.5, 1.0, 1.5) has been investigated crystallographically between 100 and 300 K using synchrotron X-ray powder diffraction and, in the case of x = 0, neutron powder diffraction.Comment: 14 pages, 9 figure

Static and resonant properties of decorated square kagome lattice compound KCu7_7(TeO4_4)(SO4_4)5_5Cl

The magnetic subsystem of nabokoite, KCu$_7$(TeO$_4$)(SO$_4$)$_5$Cl, is constituted by buckled square kagome lattice of copper decorated by quasi-isolated Cu$^{2+}$ 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 broad hump at about 150 K inherent for low-dimensional magnetic systems and evidences sharp peak at antiferromagnetic phase transition at $T_N = 3.2$K. The $C_p(T)$ curve also exhibits sharp peak at $T_N$ readily suppressed by magnetic field and additional peak-like anomaly at $T_\textrm{peak}= 5.7$ 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 kagome lattice [J.Richter, O.Derzhko and J.Schnack, Phys. Rev. B 105, 144427 (2022)]. According to position of $T_\textrm{peak}$, the leading exchange interaction parameter $J$ in nabokoite is estimated to be about 60K. ESR spectroscopy provides indications that antiferromagnetic structure below $T_N$ is non-collinear. These complex thermodynamic and resonant properties signal the presence of two weakly coupled magnetic subsystems in nabokoite, namely spin-liquid with large singlet-triplet gap and antiferromagnet represented by decorating ions. 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 kagome lattice.Comment: 13 pages, 13 figure

Quasi-1D XY Antiferromagnet Sr2Ni(SeO3)2Cl2 at Sakai-Takahashi Phase Diagram

Uniform quasi-one-dimensional integer spin compounds are of interest as a potential realization of the Haldane conjecture of a gapped spin liquid. This phase, however, has to compete with magnetic anisotropy and long-range ordered phases, the implementation of which depends on the ratio of interchain J′ and intrachain J exchange interactions and both uniaxial D and rhombic E single-ion anisotropies. Strontium nickel selenite chloride, Sr2Ni(SeO3)2Cl2, is a spin-1 chain system which passes through a correlations regime at Tmax ~ 12 K to long-range order at TN = 6 K. under external magnetic field it experiences the sequence of spin-flop at Bc1 = 9.0 T and spin-flip transitions Bc2 = 23.7 T prior to full saturation at Bsat = 31.0 T. Density functional theory provides values of the main exchange interactions and uniaxial anisotropy which corroborate the experimental findings. The values of J′/J = 0.083 and D/J = 0.357 place this compound into a hitherto unoccupied sector of the Sakai-Takahashi phase diagram. © 2021, The Author(s).Support by the P220 program of Government of Russia through the project 075-15-2021-604 is acknowledged. ANV acknowledges support by the RFBR Grant 19-02-00015. Work at Heidelberg was supported by BMBF via the project SpinFun (13XP5088) and by Deutsche Forschungsgemeinschaft (DFG) under Germany’s Excellence Strategy EXC2181/1-390900948 (the Heidelberg STRUCTURES Excellence Cluster) and through project KL 1824/13-1. We acknowledge the support of the HLD-HZDR, member of the European Magnetic Field Laboratory (EMFL). Theoretical calculations using density functional theory were supported by the Russian Science Foundation via project 20-62-46047. Experimental research was supported by the Russian Science Foundation via project 19-42-02010

Interplay of rare-earth and transition-metal subsystems in Cu<inf>3</inf>Yb(SeO<inf>3</inf>)<inf>2</inf>O<inf>2</inf>Cl

©2017 American Physical Society We present the synthesis and the experimental and theoretical study of the new member of the francisite family, Cu 3 Yb(SeO 3 ) 2 O 2 Cl. The compound reaches an antiferromagnetic order at T N = 36.7 K and experiences first-order spin-reorientation transition to weakly ferromagnetic phase at T R = 8.7 K evidenced in specific heat C p and magnetic susceptibility χ measurements. Distinctly different magnetization loops in T < T R and T R < T < T N temperature ranges reflect the interplay of rare-earth and transition-metal subsystems. At low temperatures, the saturation magnetization M s ∼ 5.2 μ B is reached in pulsed magnetic-field measurements. The electron spin resonance data reveal the complicated character of the absorption line attributed to response from both copper and ytterbium ions. Critical broadening of the linewidth at the phase transitions points to quasi-two-dimensional character of the magnetic correlations. The spectroscopy of Yb 3+ ions evidences splitting of the lowest-energy Kramers doublet of 2 F 5 / 2 excited multiplet at T R < T < T N while the ground Kramers doublet splits only at T < T R . We describe the magnetic properties both above and below the spin-reorientation transition in the framework of a unified approach based on the mean-field approximation and crystal-field calculations

The synthesis and crystal structures of the first rare-earth alkaline-earth selenite chlorides MNd10(SeO3)(12)Cl-8 (M = Ca and Sr)

Two new alkaline-earth Nd selenite chlorides MNd10(SeO3)(12)Cl-8 (M = Ca, Sr) were obtained using crystal growth from alkaline-earth chloride melts in quartz tubes. These new compounds crystallize in the orthorhombic system in space group C cca (# 68). The compounds were studied by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. It was shown that both compounds adopt the same structure type, constructed by complex [M-11(SeO3)(12)](8+) slabs separated by chloride anion layers perpendicular to the longest cell parameter. The SeO3 groups show a pyramidal shape and may be described as SeO3E tetrahedra. Such SeO3 groups decorate the Nd-O skeletons forming the [M-11(SeO3)(12)](8+) slabs. (C) 2007 Elsevier Inc. All rights reserved.</p