Evolution of Fermi surface properties in CexLa1-xB6 and PrxLa1-xB6

We report the de Haas-van Alphen (dHvA) effect measurements of the Fermi surface properties in LaB6, CexLa1-xB6 (x=0.1, 0.25, 0.5, 0.75, 1.0) and PrxLa1-xB6 (x=0.25, 0.5, 0.75, 1.0) with particular attention to the spin dependence of the Fermi surface properties. The Fermi surface shape and dimension ofCexLal-xB6 change considerably with Cc concentration, while those of PrxLa1-xB6 change very slightly up to x=0.75, and in PrB6 the Fermi surface splits into the up and down spin Fermi surfaces. The effective mass of CexLa1-xB6 increases considerably with Ce concentration and is nearly proportional to the number of Ce ions, whereas that of PrxLa1-xB6 increases slightly with Pr concentration. In CexLa1-xB6 the effective mass depends very strongly on field and increases divergently with decreasing field, while that of PrxLa1-xB6 increases slightly with decreasing field. The contribution to the dHvA signal from the conduction electrons of one spin direction diminishes with Cc concentration and appears to disappear somewhere around x=0.25-0.5. A weak spin dependence is also found in PrxLa1-xB6. The behaviors of CexLa1-xB6 and PrxLa1-xB6 are compared to discuss the origin of the spin dependence of the Fermi surface properties.