Breakdown of Chemical Scaling for Pt-Doped CaFe2As2
Breakdown of Chemical Scaling for Pt-Doped CaFe2As2
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DOI：
10.1143/jpsj.81.035002
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发表时间：
2012-02
影响因子：
1.7
通讯作者：
K. Kudo;M. Kobayashi;Satomi Kakiya;M. Danura;M. Nohara
中科院分区：
文献类型：
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作者：
K. Kudo;M. Kobayashi;Satomi Kakiya;M. Danura;M. Nohara
共掺杂CaFe2As2的电子相图捕捉到了铁基超导体的一般特征。母体化合物CaFe2As2在温度为TN = 170 K下冷却后，从顺磁性金属（PM）相转变为反铁磁性金属（AFM）相，如图1(a)所示。4几乎同时，体系在Ts处呈现出从四方相到正交相的结构相变。4 Co对Fe的部分化学取代抑制了AFM和正交相，并出现了超导相。Ca(Fe1−xCox)2As2在Co的临界浓度x≃0.06附近的最大超导转变温度为Tc = 20 K，此时原子力显微镜的有序性被完全抑制。进一步掺杂后，超导相消失。添加的CaFe2As2相图相似；5然而，AFM相被抑制并出现超导相的Ni临界浓度几乎是共掺杂CaFe2As2的一半，如图1(a)所示。上述观察结果表明，TN、Ts和Tc对掺杂水平x的依赖关系可以用掺杂过渡金属（TM）与铁之间价电子数的差异来解释，即电子相图的化学标度。对于不同tm的SrFe2As2和BaFe2As2，已经报道了这种缩放。在本文中，我们报道了化学掺杂x对pt掺杂的CaFe2As2的TN结垢的分解。我们证明，AFM相持续存在，直到Pt含量x达到其溶解度极限0.08。这种行为与Ni掺杂的CaFe2As2相矛盾，其中AFM在x = 0.03时被抑制，尽管Ni和Pt都是
The electronic phase diagram of Co-doped CaFe2As2 captures the generic features of iron-based superconductors. The parent compound CaFe2As2 exhibits a phase transition from a paramagnetic metal (PM) phase to an antiferromagnetic metal (AFM) one upon cooling at a transition temperature TN = 170 K, as shown in Fig. 1(a). 4 Almost simultaneously, system exhibits a structural phase transition from a tetragonal phase to an orthorhombic one at Ts. 4 The partial chemical substitution of Co for Fe suppresses the AFM and orthorhombic phase, and a superconducting phase appears. The maximum superconducting transition temperature Tc = 20 K is observed near the critical concentration of Co, i.e., x ≃ 0.06, at which the AFM ordering is completely suppressed in Ca(Fe1−xCox)2As2. 4 The superconducting phase disappears on further doping. Nidoped CaFe2As2 shows similar phase diagram; 5 however, the critical concentration of Ni, at which the AFM phase is suppressed and superconducting phase appears, is almost half of that for Co-doped CaFe2As2, as shown in Fig. 1(a). The above-mentioned observations imply that the dependence of TN, Ts, and Tc on the doping level x can be interpreted in terms of the difference in the number of valence electrons between the doped transition metal (TM) and iron, 7 namely, the chemical scaling of the electronic phase diagram. Such scaling has been reported for SrFe2As2 as well as BaFe2As2 with different TMs. 7 In this paper, we report a breakdown of the scaling of TN on chemical doping x for Pt-doped CaFe2As2. We demonstrate that the AFM phase persists until the Pt content x reaches its solubility limit at 0.08. This behavior is contradictory to that of Ni-doped CaFe2As2, in which the AFM is suppressed at x = 0.03, although both Ni and Pt are