Heavy-fermion behavior in YbCu 5 − x Ag x s
Heavy-fermion behavior in YbCu 5 − x Ag x s
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YbCu 5 − x Ag x s 中的重费米子行为
DOI：
10.1103/physrevb.55.1032
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发表时间：
1997
影响因子：
3.7
通讯作者：
G. Hilscher
中科院分区：
文献类型：
--
作者：
N. Tsujii;J. He;Kenichi Yoshimura;K. Kosuge;H. Michor;K. Kreiner;G. Hilscher
研究了${\mathrm{YbCu}}_{5\mathrm{\ensuremath{-}}\mathrm{x}}$体系的相关系和物性随温度和组成x的变化关系。粉末X-射线衍射实验表明，${\mathrm{YbCu}}_{5\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathm{Ag}}_{\mathm{x}}$结晶成晶态。0.125\ensuremath{\leqslant}x\ensuremath{\leqslant}1.0.范围内立方${\mathm{aube}}_{5}$型结构的单相磁化率、电阻率和比热测量表明，该体系属于一系列致密的近藤化合物，近藤效应的特征温度随x的减小而向较低的温度移动。还观察到零温下的磁化率、电阻率系数A和电比热系数α。随着x(0.125\ensuremath{\leqslant}x\ensuremath{\leqslant}1.0).的减小而增强当x=0.125时，随着x的减小，保证数学{\Gamma}值从210mJ/mol值单调增加到460mJ/mol${\mathm{K}}^{2}$，这可以用化学压力效应来解释。此外，在静水压力下，随化学压力变化的系数A与x=1.0时的系数A很好地平行。在0.0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.1，的组成范围内，该系统由两个相组成，即立方的${\mathm{AuBe}}_{5}$结构和六方的${\mathm{CaCu}}_{5}$结构。这些结果表明，尽管到目前为止只有六方的${\mathm{CaCu}}_{5}$类型的${\mathm{ybCu}}_{5}$类型的报道，但是${\mathm{YbCu}}_{5}$具有立方的${\mathm{Aube}}_{5}$结构和六方的${\mathm{CaCu}}_{5}$类型的结构。从${\mathrm{YbCu}}_{5\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathm{Ag}}_{\mathm{x}}$(0.125\ensuremath{\leqslant}x\ensuremath{\leqslant}1.0)到x=0的数学{\Gamma}值外推，假设的单相立方体${\mathm{YbCu}}_{5}$的保证数学{\Gamma}值有望达到约500mJ/摩尔${\mathm{K}}^{2}$。
The phase relation and physical properties of the ${\mathrm{YbCu}}_{5\mathrm{\ensuremath{-}}\mathrm{x}}$ ${\mathrm{Ag}}_{\mathrm{x}}$ system have been investigated as functions of temperature and composition x. Powder x-ray-diffraction experiments showed that ${\mathrm{YbCu}}_{5\mathrm{\ensuremath{-}}\mathrm{x}}$ ${\mathrm{Ag}}_{\mathrm{x}}$ crystallizes in a single phase of the cubic ${\mathrm{AuBe}}_{5}$ -type structure in the range of 0.125\ensuremath{\leqslant}x\ensuremath{\leqslant}1.0. Magnetic susceptibility \ensuremath{\chi}, electrical resistivity \ensuremath{\rho}, and specific heat C measurements revealed that this system belongs to a series of dense Kondo compounds, and the characteristic temperature of Kondo effect shifts to lower temperatures with decreasing x. It was also observed that the susceptibility at zero temperature, \ensuremath{\chi}(0), the ${\mathrm{T}}^{2}$ coefficient of resistivity, A, and the electronic specific heat coefficient, \ensuremath{\gamma}, are enhanced with the decrease of x (0.125\ensuremath{\leqslant}x\ensuremath{\leqslant}1.0). The \ensuremath{\gamma} value increases monotonically from 210 mJ/mol ${\mathrm{K}}^{2}$ for x=1.0 to 460 mJ/mol ${\mathrm{K}}^{2}$ for x=0.125 with decreasing x. This substantial increase of \ensuremath{\gamma} with decreasing x can be explained by the 'chemical pressure' effect, which is estimated from the composition dependence of the lattice parameters. Furthermore, the coefficient A depending on 'chemical pressure' is well parallel to that for x=1.0 under hydrostatic pressures. In the composition range of 0.0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.1, the system consists of two phases with the cubic ${\mathrm{AuBe}}_{5}$ -type and the hexagonal ${\mathrm{CaCu}}_{5}$ -type structures. These results mean that the ${\mathrm{YbCu}}_{5}$ exists with the cubic ${\mathrm{AuBe}}_{5}$ -type structure as well as with the hexagonal ${\mathrm{CaCu}}_{5}$ -type one, although only the hexagonal ${\mathrm{CaCu}}_{5}$ -type ${\mathrm{YbCu}}_{5}$ has been reported so far. The value of \ensuremath{\gamma} for the hypothetical cubic ${\mathrm{YbCu}}_{5}$ of single phase is expected to reach about 500 mJ/mol ${\mathrm{K}}^{2}$ from an extrapolation of the \ensuremath{\gamma} values of ${\mathrm{YbCu}}_{5\mathrm{\ensuremath{-}}\mathrm{x}}$ ${\mathrm{Ag}}_{\mathrm{x}}$ (0.125\ensuremath{\leqslant}x\ensuremath{\leqslant}1.0) to x=0.