Magnetic field dependence of the cyclotron mass in the Kondo lattice CeB6

The conduction-electron mass in the Kondo lattice system CeB6 is found to be strongly field dependent. CeB6 is an ordered heavy moment electron system with a zero field electronic specific heat coefficient of about 250 mJ/mole K2. Using the de Haas-van Alphen effect at temperatures as low as 60 mK in steady magnetic fields as large as 22 T, we observe a cyclotron orbit of frequency 8 680 T for fields along the [100] direction. The mass of this orbit was measured at eight fixed fields and found to decrease from 18 to 8 me as the field increases from 12 to 22 T. The field dependence of the cyclotron mass is consistent with recent specific heat results. The Fermi surface geometry is similar to that of LaB6, except that the extremal cross-sectional areas observed are 10 % larger than in LaB6. The f-electrons are therefore largely local rather than itinerant in CeB6, a picture confirmed by bandstructure calculations. The geometry of the Fermi surface does not depend on field. The observed field dependence of the cyclotron mass is consistent with the low energy scale of the system as measured, for example, by the Kondo temperature.