De Haas-van Alphen Effect of Heavy Electron Systems with non-Fermi Liquid behavior

本文拟利用de Haas-van Alphen （dHvA）效应对具有非费米液体行为的重电子体系CeNi2Ge2进行费米表面研究。研究了极低残余电阻率晶体生长的方法。此外，我们还测量了标准物质LaNi2Ge2的dHvA效应。结果：采用电输运法对原料铈进行预纯化，可获得高质量的单晶。2)使用种子沿[001]方向生长。最佳试样仅在距单晶棒颈点20mm处获得，其残余电阻率为1.5 μΩ cm， x射线摇摆曲线（004）反射半宽为0.2度。可能是由于其电子质量较大，所以无法观察到CeNi2Ge2的dHvA效应。将来我们将尝试在低于3He的温度下进行观测。另一方面，我们成功地测量了LaNi2Ge2的dHvA效应，并与计算得到的费米面进行了比较，得到了实验与能带计算非常吻合的结果。我们还利用非弹性中子散射和电阻率研究了磁相关性和超导性。在温度低于30 K时，发现了弱的反铁磁相关性，在环境压力和温度低于300 mK时，在2 ~ 5 GPa的压力下也发现了超导性。

The Fermi surface study of CeNi2Ge2, which is a heavy electron system showing non-Fermi liquid behavior, by means of de Haas-van Alphen (dHvA) effect was intended. The method of crystal growth with very low residual resistivity was studied. Further, we perfoemed to measure the dHvA effect of the reference material LaNi2Ge2.RESULTS : A good quality single crystals could be obtained in the following conditions : 1) Pre-purification of the raw material of Ce using electro-transport method. 2) Growth along the [001] direction using the seed. For the best specimen, which was only obtained at the position up to 20 mm from the neck point of the single crystal rod, the residual resistivity was 1.5 μΩ cm and the half width of the X-ray rocking curve, (004) reflection, was 0.2 degrees. The dHvA effect of CeNi2Ge2 could not be observed, probably due to the heavy electron masses. We will try to observe at a temperatures lower than 3He temperature in a future. On the other hand, we suceeded to measure the dHvA effect of LaNi2Ge2, and compared to the Fermi surfaces calculated, obtaining very good agreement between the experiment and the band calculaion.We also studied the magnetic correlation and the superconductivity, using the inelastic nutron scattering and the electrical resistivity. It was found the weak antiferromagnetic correlation exists at temperatures lower than 30 K, and the superconductivity also was found at ambient pressure and at pressures from 2 GPa to 5 GPa at temperatures lower than 300 mK.