Magnetic Phase Transitions fo Rare Earth Compounds Studied by the de Haas-van Alphen Effect

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The de Haas-van Alphen (dHvA) effect is the most useful method to determine the Fermi surface, cyclotron mass and scattering lifetime of the conduction electron. We have grown high-purity single crystals and studied the magnetic phase transitions of the rare earth compound by the dhvA method. We have found three kinds of phase transitions. Experimental results are as follow ;(1) Metamagnetic transition in the antiferromagnetic compoundWe have studied the dhvA effect of the antiferromagnetic compound NdIn_3. The Fermi surface in the antiferromagnetic state is found to be constructed by the band folding procedure of the Fermi surface of LaIn_3 into the small Brillouin zone based on the large magnetic unit cell.(2) Metamagnetic transition based on the quadrupole moment in PrCu_2We have found a new type of metamagnetic transition in PrCu_2 when the field is directed along the c-axis of the orthorhombic structure. Here, PrCu_2 is not an antiferromagnetic compound but a Van-Vlec para-magnetic compound with the singlet ground state of the 4f level. This transition brings about the switching of the easy (a-axis) and hard (c-axis) axs in magnetization.Change of the 4f electron nature from itinerant to localized in CeRu_2Si_2The metamagnetic behavior is found at 8T in CeRu_2Si_2 when the field is directed along the [001] direction in the tetragonal structure. We have studied in detail the dHvA experiments in fields up to 19T and at temperatures down to 20mK and clarified the Fermi surface. the 4f-electron is found to be changed in nature from itinerant to localized.