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We present the magnetic, thermodynamic, and muon spin relaxation ( $\mu \mathrm{SR}$ ) results of the dimer-based triangular antiferromagnet ${\mathrm{Ba}}_6{\mathrm{Y}}_2{\mathrm{Rh}}_2{\mathrm{Ti}}_2{\mathrm{O}}_{17-\delta }$ . The magnetic susceptibility data show the sub-Curie-Weiss behavior $\chi \left(T\right)\propto T^{-{\alpha }_{\chi }}$ below 100 K, suggesting random magnetism. The isothermal magnetization results reveal the presence of weakly interacting structural orphanmore » spins about $6.1\%$ at 2 K, arising from the oxygen deficiency. The comprehensive $\mu \mathrm{SR}$ experiments exhibit the coexisting relaxing and nonrelaxing components along with the thermally activated behavior in the muon spin relaxation rate, reflecting the fluctuating orphan spins in the dimer singlet background. In addition, we observe the scaling behavior of $M(H,T)$ in $H/T$ and $P_z\left(t\right)$ in $t/H_{\text{LF}}$ with the scaling exponents ${\alpha }_{\chi }={\alpha }_{\text{M}}=0.75$ and ${\alpha }_{\mu }=0.72$ , respectively, but not for the magnetic specific heat data. The failure of the scaling relation in $C_{\text{m}}(H,T)/T$ implies low-energy excitations dressed by the conventional orphan spins. Based on these observations, we find that the magnetic ground state resembles random singlets and discuss the possible configurations of the spin dimer unit ${\mathrm{Rh}}_2{\mathrm{O}}_9$ . Our results shed light on the role of quenched disorder in the dimer-based frustrated magnets. Published by the American Physical Society 2024« less

Kagome lattice has been actively studied for the possible realization of frustration-induced two-dimensional flat bands and a number of correlation-induced phases. Currently, the search for kagome systems with a nearly dispersionless flat band close to the Fermi level is ongoing. Here, by combining theoretical and experimental tools, we present Sc₃Mn₃Al₇Si₅ as a novel realization of correlation-induced almost-flat bands in the kagome lattice in the vicinity of the Fermi level. Our magnetic susceptibility, ²⁷Al nuclear magnetic resonance, transport, and optical conductivity measurements provide signatures of a correlated metallic phase with tantalizing ferromagnetic instability. Our dynamical mean-field calculations suggest that such ferromagneticmore » instability observed originates from the formation of nearly flat dispersions close to the Fermi level, where electron correlations induce strong orbital-selective renormalization and manifestation of the kagome-frustrated bands. In addition, a significant negative magnetoresistance signal is observed, which can be attributed to the suppression of flat-band-induced ferromagnetic fluctuation, which further supports the formation of flat bands in this compound. These findings broaden a new prospect to harness correlated topological phases via multiorbital correlations in 3d-based kagome systems.« less