Crystal structure and electronic and magnetic properties of the bilayered rhodium oxide Sr 3 Rh 2 O 7

The bilayered rhodium oxide Sr 3 Rh 2 O 7 was synthesized by high-pressure and high-temperature heating techniques. The single-phase polycrystalline sample of Sr 3 Rh 2 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 Sr 3 Rh 2 O 7 [Bbcb,a=5.4744(8) A, b =5.4716(9) A, c=20.875(2) A] is isostructural to the metamagnetic metal Sr 3 Ru 2 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 Sr 3 Rh 2 O 7 to be metallic with enhanced paramagnetism, similar to Sr 3 Ru 2 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.