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Register a new userStructure and magnetic properties of melilite-type compounds RE2Be2GeO7 (RE = Pr, Nd, Gd-Yb) with Rare-Earth ions on Shastry-Sutherland lattice
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Rare-earth (RE) based frustrated magnets as typical systems of combining strong spin-orbit coupling, geometric frustration and anisotropic exchange interactions, can give rise to diverse exotic magnetic ground states such as quantum spin liquid (QSL). The discovery of new RE-based frustrated materials is crucial for exploring the exotic magnetic phases. Herein, we report the synthesis, structure and magnetic properties of a family of melilite-type RE2Be2GeO7 (RE = Pr, Nd, Gd-Yb) compounds crystallized in a tetragonal structure, where magnetic RE3+ ions lay out on Shastry-Sutherland lattice (SSL) within ab-plane and are well separated by nonmagnetic GeBe2O7 polyhedrons along c-axis. Temperature-dependent susceptibilities and isothermal magnetization M(H) measurements reveal that most RE2Be2GeO7 compounds except RE=Tb show no magnetic ordering down to 2 K despite the dominant antiferromagnetic (AFM) interactions, where Tb2Be2GeO7 undergoes AFM transition with Neel temperature TN~ 2.5 K and field-induced spin flop behaviors (T< TN). In addition, the calculated magnetic entropy change from the isothermal M(H) curves reveal a viable magnetocaloric effect (MCE) for RE2Be2GeO7 (RE =Gd, Dy) in liquid helium temperature regimes, Gd2Be2GeO7 shows maximum Sm up to 54.8 J K-1 Kg-1 at H= 7 T and Dy2Be2GeO7 has largest value Sm=16.1 J K-1 kg-1 at H= 2 T in this family. More excitingly, rich diversity of RE ions in this family enables an archetype for exploring exotic quantum magnetic phenomena with large variability of spin located on SSL lattice.
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In the presence of a magnetic field frustrated spin systems may exhibit plateaus at fractional values of saturation magnetization. Such plateau states are stabilized by classical and quantum mechanisms including order-by-disorder, triplon crystallization, and various competing order effects. In the case of electrically conducting systems, free electrons represent an incisive probe for the plateau states. Here we study the electrical transport of Ising-type rare earth tetraborides $R$B$_4$ ($R=$Er, Tm), a metallic Shastry-Sutherland lattice showing magnetization plateaus. We find that the longitudinal and transverse resistivities reflect scattering with both the static and dynamic plateau structure. We model these results consistently with the expected strong uniaxial anisotropy in a quantitative level, providing a framework for the study of plateau states in metallic frustrated systems.
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