Abstract:

The recent discovery of iron-based superconductors has triggered intense interests in the homolo- gous rare-earth iron pnictides. These materials have the same layered structure and exhibit a number of exotic magnetic phases in addition to the unconventional superconductivity. Here we discuss the common origin of the ordered or disordered magnetic phases in the parent compounds based on an extended Anderson lattice model where hybridizations of the pnictogen 4p-orbital with both the iron 3d-orbital and the rare-earth 4f-orbital are taken into account. We show that in the strong correlation limit the model exhibits a striped antiferromagnetic long-range order for the d-electrons of irons due to the geometric frustration bridged by pnictogen atoms. The magnetic moment of the d-electrons deceases with increasing itinerancy (or decreasing correlation) of d-electrons, resulting in a quantum phase transition with a peculiar quantum criticality different to the one induced by electron doping. Associated with this transition is a heavy fermion instability driven by the hy- bridization between pnictogen 4p-orbital and rare-earth 4f-orbital. We discuss the relevance of this hybridization to several homogous rare-earth iron pnictides including CeOFeAs and CeOFeP.
 
 
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