Barlowite ${\mathrm{Cu}}_4{\left(\mathrm{OH}\right)}_6\mathrm{FBr}$ shows three-dimensional (3D) long-range antiferromagnetism, which is fully suppressed in ${\mathrm{Cu}}_3\mathrm{Zn}{\left(\mathrm{OH}\right)}_6\mathrm{FBr}$ with a kagome quantum spin liquid ground state. Here we report systematic studies on the evolution of magnetism in the ${\mathrm{Cu}}_{4-x}{\mathrm{Zn}}_x{\left(\mathrm{OH}\right)}_6\mathrm{FBr}$ system as a function of $x$ to bridge the two limits of ${\mathrm{Cu}}_4{\left(\mathrm{OH}\right)}_6\mathrm{FBr}(x=0)$ and ${\mathrm{Cu}}_3\mathrm{Zn}{\left(\mathrm{OH}\right)}_6\mathrm{FBr}(x=1)$. Neutron-diffraction measurements reveal a hexagonal-to-orthorhombic structural change with decreasing temperature in the $x=0$ sample. While confirming the 3D antiferromagnetic nature of low-temperature magnetism, the magnetic moments on some ${\mathrm{Cu}}^{2+}$ sites on the kagome planes are found to be vanishingly small, suggesting strong frustration already exists in barlowite. Substitution of interlayer ${\mathrm{Cu}}^{2+}$ with ${\mathrm{Zn}}^{2+}$ with gradually increasing $x$ completely suppresses the bulk magnetic order at around $x=0.4$ but leaves a local secondary magnetic order up to $x\sim 0.8$ with a slight decrease in its transition temperature. The high-temperature magnetic susceptibility and specific-heat measurements further suggest that the intrinsic magnetic properties of kagome spin liquid planes may already appear from $x>0.3$ samples. Our results reveal that the ${\mathrm{Cu}}_{4-x}{\mathrm{Zn}}_x{\left(\mathrm{OH}\right)}_6\mathrm{FBr}$ may be the long-thought experimental playground for the systematic investigations of the quantum phase transition from a long-range antiferromagnet to a topologically ordered quantum spin liquid.

CdO : Ag nanocomposites with metallic Ag nanoparticles embedded in the polycrystalline CdO matrix were synthesized by the solid-state reaction method. The addition of Ag led to increased grain boundaries of CdO and created numerous CdO/Ag interfaces. By incorporating Ag into the CdO matrix, the power factor was increased which was probably due to the carrier energy filtering effect induced by the enhanced energy-dependent scattering of electrons. In addition, reduced thermal conductivity was also achieved by stronger phonon scattering from grain boundaries, CdO/Ag interfaces and Ag nanoparticles. These concomitant effects resulted in enhanced ZT values for all CdO : Ag nanocomposites, demonstrating that the strategy of introducing metallic Ag nanoparticles into the CdO host was very effective in optimizing the thermoelectric performance.

Powder neutron-diffraction experiments have been employed to establish the effects of site-selective magnetic dilution in the ${\mathrm{Sm}}_2{\mathrm{MnMnMn}}_{4-x}{\mathrm{Ti}}_x{\mathrm{O}}_{12} A$-site columnar ordered quadruple perovskite manganites ($x=1, x=2$, and $x=3$). We show that in all three compositions the Mn ions adopt a collinear ferrimagnetic structure below 27, 62, and 34 K, respectively. An unexpected increase in the ordering temperature was observed between the $x=1$ and $x=2$ samples, which indicates a considerable departure from mean-field behavior. This result is corroborated by large reductions in the theoretical ground-state magnetic moments observed across the series, which indicate the presence of spin fluctuations and/or disorder. We show that long-range magnetic order in the $x=3$ sample, which occurs below the percolation threshold for B-B exchange, can only be understood to arise if it is mediated via both A-B and B-B exchange, hence confirming the importance of A-B exchange interactions in these materials. Finally, we show that site-selective magnetic dilution enables the tuning of a ferrimagnetic compensation point and the introduction of temperature-induced magnetization reversal.