Jin C-Q, Zhou J-S, Goodenough J B, Liu Q Q, Zhao J G, Yang L X, Yu Y, Yu R C, Katsura T, Shatskiy A, Ito E
Institute of Physics, Chinese Academy of Science, Beijing 100080, China.
Proc Natl Acad Sci U S A. 2008 May 20;105(20):7115-9. doi: 10.1073/pnas.0710928105. Epub 2008 May 14.
The cubic perovskite BaRuO(3) has been synthesized under 18 GPa at 1,000 degrees C. Rietveld refinement indicates that the new compound has a stretched Ru-O bond. The cubic perovskite BaRuO(3) remains metallic to 4 K and exhibits a ferromagnetic transition at T(c) = 60 K, which is significantly lower than the T(c) approximately = 160 K for SrRuO(3). The availability of cubic perovskite BaRuO(3) not only makes it possible to map out the evolution of magnetism in the whole series of ARuO(3) (A = Ca, Sr, Ba) as a function of the ionic size of the A-site r(A,) but also completes the polytypes of BaRuO(3). Extension of the plot of T(c) versus r(A) in perovskites ARuO(3) (A = Ca, Sr, Ba) shows that T(c) does not increase as the cubic structure is approached, but has a maximum for orthorhombic SrRuO(3). Suppressing T(c) by Ca and Ba doping in SrRuO(3) is distinguished by sharply different magnetic susceptibilities chi(T) of the paramagnetic phase. This distinction has been interpreted in the context of a Griffiths' phase on the (Ca Sr)RuO(3) side and bandwidth broadening on the (Sr,Ba)RuO(3) side.
立方钙钛矿型BaRuO₃在18吉帕斯卡压力和1000摄氏度条件下合成。里特韦尔德精修表明新化合物存在拉伸的Ru - O键。立方钙钛矿型BaRuO₃在4K时仍为金属态，并在Tc = 60K时呈现铁磁转变，这明显低于SrRuO₃的Tc约160K。立方钙钛矿型BaRuO₃的可得性不仅使得描绘整个ARuO₃系列（A = Ca、Sr、Ba）中磁性随A位离子尺寸r(A)的演变成为可能，还完善了BaRuO₃的多型体。在钙钛矿型ARuO₃（A = Ca、Sr、Ba）中绘制Tc与r(A)的关系图表明，Tc并非随着接近立方结构而增加，而是在正交晶系的SrRuO₃时达到最大值。通过在SrRuO₃中掺杂Ca和Ba来抑制Tc，其顺磁相的磁化率χ(T)有明显不同。这种差异在（Ca，Sr）RuO₃一侧的格里菲斯相和（Sr，Ba）RuO₃一侧的带宽展宽的背景下得到了解释。
