Structure and physical properties of SrNiR u5 O11 single crystals: An R -type ferrite based on ordered kagome nets

Single crystals of the R-type ferrite SrNiRu5O11 were grown from a chloride flux. The hexagonal crystal structure contains ruthenium located on distorted kagome nets. The low-temperature dc magnetic susceptibilities (χ and χ, perpendicular and parallel to the c axis, respectively) diverge as T-0.3, and do not exhibit any indication of long-range magnetic order down to 4.5 K. The electrical resistivity varies as T1.6 below 40 K, which is typical of non-Fermi liquids, and may originate from a competition between residual magnetic interactions among Ni2+ (S=1) spins and geometrical frustration on the two-dimensional kagome lattice of Ru3+ (S=) spins. The transverse magnetoresistivity ρxy at constant temperature T=5K for current (J) -magnetic field (H) configurations, JHc axis and JHc axis, reveals no anomalous contribution, which is consistent with the absence of magnetic order. Fits of the specific heat data below 10 K require a dominant, but unusual electronic term of the form Cel=γT1.2, which is expected for massless Dirac fermion states in topological insulators, or spin-liquid phases.