F -spin physics of rare-earth iron pnictides: Influence of d -electron antiferromagnetic order on the heavy-fermion phase diagram

Some of the high- Tc iron pnictides contain magnetic rare-earth elements, raising the question of how the existence and tunability of a d -electron antiferromagnetic order influences the heavy-fermion behavior of the f moments. With CeOFeP and CeOFeAs in mind as prototypes, we derive an extended Anderson lattice model appropriate for these quaternary systems. We show that the Kondo screening of the f moments are efficiently suppressed by the d -electron ordering. We also argue that, inside the d -electron ordered state (as in CeOFeAs), the f moments provide a rare realization of a quantum frustrated magnet with competing J1 - J2 - J3 interactions in an effective square lattice. Implications for the heavy-fermion physics in broader contexts are also discussed.