Spin and Magnetic Field Dependences of Quasiparticle Mass in Ferromagnetic State of Heavy Fermions

Abstract

We investigate the mechanism underlying the suppression of heavy-fermion mass enhancement in the presence of a magnetic field. In the framework of statistically consistent Gutzwiller method (SGA) we study the periodic Anderson model in the strong correlation limit. The finite-U corrections are included systematically allowing to describe the coexistence of Kondo compensation effect and ferromagnetic ordering, as well as weak delocalization of the f-electrons. In particular, we observe that the resulting mass enhancement factor of spin-up electrons and that of spin-down are not equal in ferromagnetic phases and depend strongly on the applied field and the f-level occupancy. We predict that mass enhancement for the spin-up quasiparticles is larger then that of spin-down and both of them decrease in the applied magnetic field. We argue that above features, as well as a nonmonotonic variation of the quasiparticle effective masses observed in our model are in good agreement with earlier experimental measurements for CexLa1−xB6.