High-Pressure and High-Temperature Synthesis of a Novel Perovskite Compound: Magnetic and Electric Properties of the Rho
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High-Pressure and High-Temperature Synthesis of a Novel Perovskite Compound: Magnetic and Electric Properties of the Rhodium Oxide SrRhO3 K. Yamaura,1 D.P. Young,2 and E. Takayama-Muromachi1 1 Superconducting Materials Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, JAPAN. 2 Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, U.S.A. ABSTRACT Novel perovskite compound SrRhO3 was synthesized in a polycrystalline form by high-pressure technique at 6 GPa and 1500 °C, followed by measurements of magnetic susceptibility, electrical resistivity, thermopower, and specific heat. Powder x-ray diffraction study found the slightly distorted perovskite structure, GdFeO3-type, to be likely to SrRhO3; space group was Pnma and lattice parameters were a = 5.5394(2) Å, b = 7.8539 (3) Å, and c = 5.5666(2) Å. Oxygen vacancies in the perovskite were quantitatively investigated by thermogravimetric analysis and then found either absent or at least insignificant. The title compound shows a Fermi-liquid behavior in its electrical resistivity. The magnetic susceptibility is large [χ(300) ~1.1×10-3 emu/mol-Rh], and the characteristics seem to be intermediate between enhanced Pauli- and Curie-Weiss-type paramagnetism. INTRODUCTION The series of the perovskite compound SrTrO3, where Tr represents a transition metal (IV) element, offers a fascinating field, rich with opportunities both in basic research and in potential applications. Many members in the series show metallic characteristics (Tr = V [1-3], Cr[4], Fe[5], Co[6,7], Nb[8,9], Mo[10-15], Ru[16], Rh[17], Ir[18-21]), and some of those show ferro- (Co [6,7], Ru [16]) and antiferromagnetism (Mn [22], Fe [5]). The members who have no d electrons (Ti [23,24], Zr [25], and Hf [26,27]) are electrically insulating, as simply expected. Two members SrOsO3 [28] and SrNiO3 [29-36] have been reported to be obtained, however the electronic and magnetic characteristics of those are not known to our knowledge. The current members of the SrTrO3 series are listed in figure 1. All members are not superconducting except for the oxygen-nonstoichiometric SrTiO3-z, electron doped (Sr,Nb)TiO3, and (Sr,La)TiO3 [23,24]. Unusual superconductivity was found in the closely related compound Sr2Ru4+O4, for
Figure 1. Variety of the strontium-transition-metal-oxide perovskites. The metallic compounds are designated by shades. The magnetism and structure type of each compound are indicated in the box. Characteristics of the nickel and osmium compounds may be unreported thus far. Reference numbers for each compound are shown in the text. D7.19.1
which ferromagnetic spin fluctuations play an essential role to drive electron couplings in the superconducting state blow about 1 K [37]. Recent progress in research of quantum electronic characteristics of the 4d electrons in Sr2RuO4 and Sr3Ru2O7 has suggested that a novel ground state such as the unconventional superconductivity might be stable in the vicinity of a quantum critical point, where quantum fluctua
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