Magnetic-superconducting phase diagram of Eu 2 − x Ce x RuSr 2 Cu 2 O 10 − δ
Magnetic-superconducting phase diagram of Eu 2 − x Ce x RuSr 2 Cu 2 O 10 − δ
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Eu 2 − x Ce x RuSr 2 Cu 2 O 10 − δ 的磁超导相图
DOI：
10.1103/physrevb.66.024503
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发表时间：
2001
影响因子：
3.7
通讯作者：
E. Galstyan
中科院分区：
文献类型：
--
作者：
I. Felner;U. Asaf;E. Galstyan
${\mathrm{Eu}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{RuSr}}_{2}{\mathrm{Cu}}_{2}{\mathrm{O}}_{10\ensuremath{-}\ensuremath{\delta}}$ (Ru-2122) 是第一个基于 Cu-O 的超导系统${\mathrm{CuO}}_{2}$ 平面中的 (SC) 和 Ru 亚晶格中的弱铁磁性 (WFM) 共存。 ${\mathrm{CuO}}_{2}$ 平面中的空穴掺杂通过适当改变 Ce 浓度来控制。当 Ce 含量为 0.4\char21{}0.8 时，发生 SC，当 $\mathrm{Ce}=0.6 时，最高 ${T}_{C}=35\mathrm{K}$。$ 制备的非 SC ${\mathrm{EuCeRuSr}}_{2}{\mathrm{Cu}}_{2}{\mathrm{O}}_{10}$ $(x=1)$ 样品在低于 ${T}_{\mathrm{irr}}=125\mathrm{K}$ 时表现出磁不可逆性，并在 ${T}_{M}=165\mathrm{K}$ 处具有反铁磁性 (AFM)。$ 5 K 时的饱和矩为${M}_{\mathrm{sat}}=0.89{\ensuremath{\mu}}_{B}/\mathrm{Ru}$ 接近 ${\mathrm{Ru}}^{5+} 低自旋态的预期 $1{\ensuremath{\mu}}_{B}$。$在氧气压力下退火不会影响这些参数，而氧气耗尽会使这两个参数发生变化${T}_{\mathrm{irr}}$ 和 ${T}_{M}$ 分别高达 169 和 215 K。 ${\mathrm{Eu}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{RuSr}}_{2}{\mathrm{Cu}}_{2}{\mathrm{O}}_{10\ensuremath{-}\ensuremath{\delta}}$的系统磁学研究表明${T}_{M},$ ${T}_{\mathrm{irr}},$ 和 ${M}_{\mathrm{sat}}$ 随 x 减小，并给出了完整的 Ce 相关磁 SC 相图。提出了 SC 状态的简单模型。我们在交流和直流磁性研究的框架中解释了磁性行为，并认为(i)系统在${T}_{M}处变成AFM；$(b)在${T}_{\mathrm{irr}}l{T}_{M}处，$WFM是由Ru矩的倾斜引起的：(c)在较低温度下，适当的样本在${T}_{C}处变成SC。$磁性特征不受SC状态的影响，并且这两种状态共存。
${\mathrm{Eu}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{RuSr}}_{2}{\mathrm{Cu}}_{2}{\mathrm{O}}_{10\ensuremath{-}\ensuremath{\delta}}$ (Ru-2122) is the first Cu-O-based system in which superconductivity (SC) in the ${\mathrm{CuO}}_{2}$ planes and weak ferromagnetism (WFM) in the Ru sublattice coexist. The hole doping in the ${\mathrm{CuO}}_{2}$ planes is controlled by appropriate variation of the Ce concentration. SC occurs for Ce contents of 0.4\char21{}0.8, with the highest ${T}_{C}=35\mathrm{K}$ for $\mathrm{Ce}=0.6.$ The as-prepared non-SC ${\mathrm{EuCeRuSr}}_{2}{\mathrm{Cu}}_{2}{\mathrm{O}}_{10}$ $(x=1)$ sample exhibits magnetic irreversibility below ${T}_{\mathrm{irr}}=125\mathrm{K}$ and orders antiferromagnetically (AFM) at ${T}_{M}=165\mathrm{K}.$ The saturation moment at 5 K is ${M}_{\mathrm{sat}}=0.89{\ensuremath{\mu}}_{B}/\mathrm{Ru}$ close to the expected $1{\ensuremath{\mu}}_{B}$ for the low-spin state of ${\mathrm{Ru}}^{5+}.$ Annealing under oxygen pressures does not affect these parameters, whereas depletion of oxygen shifts both ${T}_{\mathrm{irr}}$ and ${T}_{M}$ up to 169 and 215 K, respectively. Systematic magnetic studies of ${\mathrm{Eu}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{RuSr}}_{2}{\mathrm{Cu}}_{2}{\mathrm{O}}_{10\ensuremath{-}\ensuremath{\delta}}$ show that ${T}_{M},$ ${T}_{\mathrm{irr}},$ and ${M}_{\mathrm{sat}}$ decrease with x, and the full Ce-dependent magnetic-SC phase diagram is presented. A simple model for the SC state is proposed. We interpret the magnetic behavior in the framework of our ac and dc magnetic studies, and argue that (i) the system becomes AFM ordered at ${T}_{M};$ (b) at ${T}_{\mathrm{irr}}l{T}_{M},$ WFM is induced by the canting of the Ru moments: and (c) at lower temperatures, the appropriate samples become SC at ${T}_{C}.$ The magnetic features are not affected by the SC state, and the two states coexist.