Preparation and electronic properties of ${\mathrm{Sr}}_{2\mathrm{-}\mathit{x}}$${\mathrm{La}}_{\mathit{x}}$${\mathrm{RhO}}_4$

${\mathrm{K}}_2$ ${\mathrm{NiF}}_4$-type solid solution system ${\mathrm{Sr}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{La}}_{\mathit{x}}$ ${\mathrm{RhO}}_4$ was prepared and the structure and electrical and magnetic properties were investigated. The result of powder x-ray-diffraction analysis shows stretching of the a and b axes and shortening of the c axis with an increase of x. The positive temperature dependence of the resistivity in the range x≤0.15 disappears with an increase of x greater than 0.15. The temperature dependence of the activation energy of carriers suggests two-dimensional variable range hopping-type conduction in the semiconducting range. The localized magnetic moment of the Rh ion is greater than the calculated value based on the low spin state, and the antiferromagnetic interaction among Rh ions decreases with an increase of x. A magnetic anomaly around 60 K observed for ${\mathrm{Sr}}_2$ ${\mathrm{RhO}}_4$ diminishes with an increase of x and vanishes at x=0.20. A positive Seebeck coefficient suggests hole conduction in this system and the Fermi energy obtained from the linear temperature dependence of the Seebeck coefficient on T decreases with x, which can be explained from the decrease of holes with the substitution of low spin ${\mathrm{Rh}}^{3+}$(4${\mathit{d}}^6$) for ${\mathrm{Rh}}^{4+}$(4${\mathit{d}}^5$).