High-pressure synthesis of the cubic perovskite BaRuO ₃ and evolution of ferromagnetism in ARuO ₃ (A = Ca, Sr, Ba) ruthenates

Abstract

The cubic perovskite BaRuO3 has been synthesized under 18 GPa at 1,000°C. Rietveld refinement indicates that the new compound has a stretched Ru-O bond. The cubic perovskite BaRuO3 remains metallic to 4 K and exhibits a ferromagnetic transition at Tc ‫؍‬ 60 K, which is significantly lower than the Tc Ϸ 160 K for SrRuO3. The availability of cubic perovskite BaRuO3 not only makes it possible to map out the evolution of magnetism in the whole series of ARuO3 (A ‫؍‬ Ca, Sr, Ba) as a function of the ionic size of the A-site rA, but also completes the polytypes of BaRuO3. Extension of the plot of Tc versus rA in perovskites ARuO3 (A ‫؍‬ Ca, Sr, Ba) shows that Tc does not increase as the cubic structure is approached, but has a maximum for orthorhombic SrRuO3. Suppressing Tc by Ca and Ba doping in SrRuO3 is distinguished by sharply different magnetic susceptibilities (T) of the paramagnetic phase. This distinction has been interpreted in the context of a Griffiths' phase on the (Ca Sr)RuO3 side and bandwidth broadening on the (Sr,Ba)RuO3 side.magnetism ͉ compounds ͉ Ruthenate

Magnetotransport properties of BaRuO3: Observation of two scattering rates

“…Early transport measurements were carried out on 9R BaRuO 3 without identifying the structure-property relationships 17 . Following up measurements on single crystalline 4H and 9R BaRuO 3 revealed different temperature dependences of resistivity -the 4H phase is metallic while the 9R phase shows semiconducting behavior at low temperatures 12,13,16 . In addition, results obtained from optical conductivity measurements 18,19 suggest that 4H and 9R BaRuO 3 both possess a pseudogap.…”

“…Four different crystalline forms of BaRuO 3 , known as nine-layered rhombohedral (9R) 9-11 , four-layered hexagonal (4H) 10,11 , six-layered hexagonal (6H) 11 , and cubic perovskite structure (3C), have been synthesized, with the last two forms under extremely high pressures 12,13 . These structures have different amounts of corner and face sharing RuO 6 octahedra.…”

Electronic and magnetic properties of epitaxial SrRhO3 films

“…4,5 However, the synthesis of many of these compounds proved to be a formidable task, often requiring high pressure and high temperature; which in turn limited experimental efforts on many of these compounds to a few experimental studies with polycrystalline samples. [5][6][7][8][9][10] Theoretical work predicted that the magnetic ground state of the orthorhombic perovskite SrRhO 3 is sensitive to its symmetry with the bulk orthorhombic structure forming a paramagnetic (PM) metallic state, while the high symmetry cubic perovskite structure would reveal a ferromagnetic metallic state. 11 In addition, SrRhO 3 has recently received attention for the potential to realize topologically protected states as a constituent material in artificial heterostructures and superlattices.…”

Metal-Insulator Transition and Orbital Order inPbRuO3

“…All of the cubic-type ARuO 3 perovskites (A = Ca, Sr, Ba) are metallic to lowest measured temperatures. SrRuO 3 and BaRuO 3 are Stoner ferromagnets with Curie temperatures of T C = 160 and 60 K respectively [4,5,6,7], but CaRuO 3 shows non-Fermi liquid behaviour without a magnetic transition [8]. Another ruthenate perovskite, PbRuO 3 , was synthesised at high pressures in 1970 [9], but the electronic properties of this material have not been reported.…”