Fermi Surface Studies of Heavy Electron System by the de Haas-van Alphen Experiments

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We have determined the Fermi surface properties of Ce and U heavy electron systems by the de Haas-van Alphen(dHvA)experiments. The number of the compounds which we have studied is about twelve. Important dHvA results are summarized as follows ;(1)We have clarified the relation between the cyclotron mass and the scattering lifetime from the dHvA experiments of CeIn3Namely, the larger the cyclotron mass becomes, the scattering lifetime is, such that the product of the cyclotron mass and the inverse scattering lifetime is constant.(2)Another important problem in the heavy electron system is weak magnetism, which is related to the metamagnetic behavior. we have measured the magnetoresistance and the dHvA effect for LaRu_2Si_2 and CeRu_2Si_2. The Fermi surface of LaRu_2Si_2 is concluded to be an uncompensated metal, possessing a large ellipsoidal Fermi surface which occupies half of the Brillouin zone. on the other hand, CeRu_2Si_2 is a compensated metal, resulting that 4f electrons in CeRu_2Si_2 are itinerant. When the field is directed along the c-axis, metamagnetism occurs at 80 kOe. The 4f character is not clear at higher fields than 80 kOe.(3)We have succeeded in growth a high-quality single crystal of the ferromagnetic compound UGe_2. Carriers with the large cyclotron masses of 10-25m_0 were detected in our dHvA experiments.