Crystal structure and electronic and magnetic properties of the bilayered rhodium oxide ${\mathrm{Sr}}_3{\mathrm{Rh}}_2{\mathrm{O}}_7$

The bilayered rhodium oxide ${\mathrm{Sr}}_3{\mathrm{Rh}}_2{\mathrm{O}}_7$ was synthesized by high-pressure and high-temperature heating techniques. The single-phase polycrystalline sample of ${\mathrm{Sr}}_3{\mathrm{Rh}}_2{\mathrm{O}}_7$ was characterized by measurements of magnetic susceptibility, electrical resistivity, specific heat, and thermopower. The structural characteristics were investigated by powder neutron diffraction study. The rhodium oxide ${\mathrm{Sr}}_3{\mathrm{Rh}}_2{\mathrm{O}}_7$ $[Bbcb,a=5.4744\mathrm{}(8)\mathrm{}\mathrm{\AA },b=5.4716\mathrm{}(9)\mathrm{}\mathrm{\AA },c=20.875\mathrm{}(2\left)\mathrm{}\mathrm{\AA }\right]$ is isostructural to the metamagnetic metal ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7,$ with five $4d$ electrons per Rh, which is electronically equivalent to the hypothetical bilayered ruthenium oxide, where one electron per Ru is doped into the Ru-327 unit. The present data show the rhodium oxide ${\mathrm{Sr}}_3{\mathrm{Rh}}_2{\mathrm{O}}_7$ to be metallic with enhanced paramagnetism, similar to ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7.$ However, neither manifest contributions from spin fluctuations nor any traces of a metamagnetic transition were found within the studied range from 2 K to 390 K below 70 kOe.