Transport, magnetic, thermodynamic, and optical properties in Ti-doped ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$

We report on electrical resistivity, magnetic susceptibility, and magnetization on heat-capacity and optical experiments in single crystals of ${\mathrm{Sr}}_2{\mathrm{Ru}}_{1-x}{\mathrm{Ti}}_x{\mathrm{O}}_4.$ Samples with $x=0.1\mathrm{}$ and 0.2 reveal purely semiconducting resistivity behavior along c and the charge transport is close to localization within the $\mathrm{ab}$ plane. A strong anisotropy in the magnetic susceptibility appears at temperatures below 100 K. Moreover magnetic ordering in the c direction with a moment of order $0.01\hspace{0.5em}{\mu }_{\mathrm{B}}/\mathrm{f}.\mathrm{u}.\mathrm{}$ occurs at low temperatures. On doping the low-temperature linear term of the heat capacity becomes significantly reduced and probably is dominated by spin fluctuations. Finally, the optical conductivity reveals the anisotropic character of the dc resistance, with the in-plane conductance roughly following a Drude-type behavior and an insulating response along c.