Magnetic, thermal, transport, and structural properties of Sr2RuO4+ delta : Enhanced charge-carrier mass in a nearly metallic oxide.

Abstract

Measurements of electrical resistivity, magnetic susceptibility, heat capacity, and powder neutron diffraction are presented on ${\mathrm{Sr}}_{2}$${\mathrm{RuO}}_{4+\mathrm{\ensuremath{\delta}}}$. Specimens with low-impurity levels allow magnetic susceptibility in the range 5T350 K to be measured; these measurements indicate a small effective magnetic moment of ${\mathrm{\ensuremath{\mu}}}_{\mathrm{eff}}$\ensuremath{\approxeq}1${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ per Ru ion. Electrical resistivity displays nonmetallic behavior in the range 1.2T300 K with \ensuremath{\rho}(295 K)=51 m\ensuremath{\Omega} cm. A rather large linear heat-capacity coefficient of \ensuremath{\gamma}=45.6 mJ/mol ${\mathrm{K}}^{2}$ is reported; speculation is made regarding its origin. Rietveld refinement of powder-neutron-diffraction data provide insight into the physical properties and reveal interesting differences to isostructural ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$. Comparisons are drawn to other transition-metal oxides.