In this letter, we report studies on the electronic transport properties of the triple-layered ruthenate Sr4Ru3O10. We observed surprising anomalous features near its itinerant metamagnetic transition, including ultrasharp magnetoresistivity steps, a nonmetallic temperature dependence in resistivity for upward field sweeps, and a resistivity drop in temperature dependence for downward field sweeps. These features suggest that the metamagnetic transition of Sr4Ru3O10 occurs via an electronic phase separation process with magnetic domain formation.
In this letter, we report an unusual nearly ferromagnetic heavy-mass state with a surprisingly large Wilson ratio Rw (e.g., Rw∼700 for x=0.2) in double layered ruthenates (Sr1−xCax)3Ru2O7 with 0.08<x<0.4. This state does not evolve into a long-range ferromagnetically ordered state despite considerably strong ferromagnetic correlations, but it freezes into a cluster-spin glass at low temperatures. In addition, evidence of non-Fermi-liquid behavior is observed as the spin-freezing temperature of the cluster-spin glass approaches zero near x≈0.1. We discuss the origin of this unique magnetic state from the Fermi-surface information probed by Hall-effect measurements
(Sr1−xCax)3Ru2O7 is characterized by complex magnetic states, spanning from a long-range antiferromagnetically ordered state over an unusual heavy-mass nearly ferromagnetic (NFM) state to an itinerant metamagnetic (IMM) state. The NFM state, which occurs in the 0.4 >x> 0.08 composition range, freezes into a cluster spin glass (CSG) phase at low temperatures [Z. Qu et al., Phys. Rev. B 78, 180407(R) (2008)]. In this article, we present the scaling analyses of magnetization and the specific heat for (Sr1−xCax)3Ru2O7 in the 0.4 >x> 0.08 composition range. We find that in a temperature region immediately above the spin freezing temperature Tf, the isothermal magnetization M(H) and the temperature dependence of electronic specific heat Ce(T) exhibit anomalous power-law singularities; both quantities are controlled by a single exponent. The temperature dependence of magnetization M(T) also displays a power-law behavior, but its exponent differs remarkably from that derived from M(H) and Ce(T). Our analyses further reveal that the magnetization data M(H,T) obey a phenomenological scaling law of M(H,T)∝Hαf(H/Tδ) in a temperature region between the spin freezing temperature Tf and the scaling temperature Tscaling. Tscaling systematically decreases with the decease of Ca content. This scaling law breaks down near the critical concentration x= 0.1 where a CSG-to-IMM phase transition occurs. We discussed these behaviors in term of the effect of disorder on the quantum phase transition.
In this article, we report the electronic and magnetic phase diagram of Ca3(Ru1−xTix)2O7. With Ti doping, the system evolves from a quasi-two-dimensional metal with ferromagnetic (FM) bilayers coupled antiferromagnetically along the c axis (AFM-b) for x=0, to a weakly localized state for 0<x<0.05, and finally to a Mott insulator with G-type antiferromagnetic (G-AFM) order for x≥0.05. The magnetic state switching from the AFM-b to the G-AFM occurs in the weakly localized state near x=0.03. We show that such a magnetic transition is controlled by the charge carrier itinerancy and can be understood in light of competing interactions between FM double exchange and AFM superexchange. An incommensurate component is also observed due to competing magnetic interactions.