Non-Fermi Liquid phenomena in heavy-fermion Ce compounds

最近的神经元衍射实验表明，顺磁性重费米子化合物CeRu_2Si_2的Ru位被Rh取代后，Ce(Ru_<1-x>Rh_2)Si_2体系的反铁磁有序度为0.05*x*0.3，具有不对称的正弦结构（波数和矩沿c轴方向分布）。因此，在本研究项目的第一步，我们测量了当前系统的电阻率、比热和磁化率。结果表明，在Neel温度下，重准粒子带沿c轴方向出现了费米面嵌套现象，费米面部分间隙打开。因此，我们得出结论，反铁磁性是由于费米表面嵌套后的自旋密度波（SDW）跃迁。我们还测量了该体系在磁场中的电阻率、比热和磁化率。结果表明，间隙坍缩，重费米子的费米表面完全恢复为顺磁费米液态。在下一步中，我们测量了.x=0.03的电阻率和磁化率，它位于SDW和顺磁相之间的较低临界浓度区域。当x=0.35、0.375、0.40时，处于较高的临界浓度区域。对于x=0.03的类费米液体，测得磁化率与温度无关，低温时电阻率为cc T^2。另一方面，当x = 0.35、0.375和0.40时，观察到非费米-液相的温度依赖关系：磁化率* -ROO<T>，电阻率* T。因此，表明该体系在x *0.35的较高临界rh浓度区域存在非费米-液相。

Recent neuron diffraction experiment has shown that a system Ce(Ru_<1-x>Rh_2)Si_2, where Rh is substituted into the Ru site of paramagnetic heavy-fermion compound CeRu_2Si_2 with a large magnetic anisotropy along the c-axis, has an antiferromagnetic ordering for 0.05*x*0.3 with an incommensurate sinusoidal structure (the wave number and moment are along the c-axis).Thus, in the first step of this research project we measured the resistivity, specific heat and susceptibility of the present system. The results suggest that the Fermi-surface nesting occurs along the c-axis direction in the heavy quasi-particle band at the Neel temperature with Partial gap opening of the Fermi surface. Therefore, we conclude that the antiferromagnetism is due to the spin density wave (SDW) transition following the Fermi-surface nesting. We also measured the resistivity, specific heat and susceptibility of the present system in magnetic fields. The results suggest' that the gap collapse and the Fermi surface of the heavy fermion completely recovers into a paramagnetic Fermi liquid state.In the next step we measured the resistivity and susceptibility for .x=0.03, which is in the lower critical concentration region between the SDW and paramagnetic phases, . and for x=0.35, 0.375 and 0.40, which is in the higher critical concentration region. For x=0.03 Fermi-liquid like temperature dependence has been measured the susceptibility is temperature independent and the resistivity cc T^2 in the low temperature. On the other hand, for x = 0.35, 0.375 and 0.40 non-Fermi-liquid like temperature dependence has been observed : the susceptibility * -ROO<T> and the resistivity * T.Therefore, it is suggested that a non-Fermi-liquid phase exists in the higher critical Rh-concentration region of x *0.35 of this system.