De Haas-van Alphen Effect in Rare-Earth Gallium compounds.

我们改进了测量dHaas van Alphen(DHvA)效应的装置，在12T磁场中获得了温度低至0.3K的dHvA信号。利用该系统测量了稀土镓化合物PrGa2、SmGa2、GdGa2和LaGa2的HVA效应。LaGa2被认为是REGa2化合物的参考物质。测量了Yb化合物YbSn3和YbZn11以及铀化合物UGa2的dHvA效应。结果表明：(1)PrGa2和GdGa2的dHvA频率与LaGa2的dHvA频率角关系非常相似。然而，它们中的一些分支与LaGa2的分支不对应。这表明在PrGa2和GdGa2反铁磁态下形成的磁性布里渊区影响了这些化合物的能带结构，并在这些化合物中产生了新的费米面。(2)SmGa2的结果与LaGa2的结果大不相同：在LaGa2中观察到的费米面在[001]方向的多重连接被完全打破。这表明，在费米能级以上的4f2能级与S、p和d带混合，Sm离子的价态部分在2-3之间波动。(3)在PrGa2和CeGa2中观察到的与晶格不相称的调制磁结构的起源是由于费米面的嵌套效应。调制磁结构的波数与嵌套效应的嵌套矢量相一致。我们继续研究其他稀土化合物和铀化合物的dHvA效应，以了解4f和5f电子对磁性和重电子性质的影响。

We have improved the apparatus for measuring de Haas van Alphen (dHvA) effect to obtain the dHvA Signal at temperature as low as 0.3K in magnetic fields of 12T with the aid of Grant-in-Aid of Scientific Research. Using this system we have measured the HvA effect of the rare-earth (RE) gallium compounds of PrGa2, SmGa, GdGa2 and LaGa2. The LaGa2 is known as the reference material of REGa2 compounds. The measurements of dHvA effects were also made on the ytterbium compounds YbSn3 and YbZn11 and the uranium compound UGa2. the gross features of the results are as follows : (1) The angular dependences of dHvA frequencies of PrGa2 and GdGa2 are very similar to that of LaGa2. There are however some branches in them that are not corresponding to that of LaGa2. This shows that the magnetic Brillouin zones formed in antiferromagnetic states of PrGa2 and GdGa2 affect the band structures of these compounds and create the new Fermi surfaces in these compounds. (2) The results in SmGa2 are very different to that of LaGa2 : the multiple connection of Fermi surface in the [001] direction observed in LaGa2 is completely broken. This indicates that 4f2+level just above the Fermi level mixes with the s, p and d bands and the valence of Sm ion is partly fluctuated between 2+ and 3+. (3) The origin of the modulated magnetic structure incommensurate with the lattice observed in PrGa2 and CeGa2 is found to be due to the nesting effect of the Fermi surface. The wave numbers of the modulated magnetic structures agree with the nesting vector of the nesting effect.We continue to investigate the dHvA effect of other RE compounds as well as uranium compound to understand the effect of 4f and 5f electrons on magnetic and heavy electron properties.