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摘要
Recent Fe x-ray emission spectroscopy experiments [H. Gretarsson et al., Phys. Rev. B 84, 100509 (2011)] unveiled sizable local moments in iron pnictides in the room-temperature paramagnetic state. In an effort to further clarify the notion of coexisting magnetic moments and itinerant carriers in iron pnictides we focus on the interactions between the two subsystems. At a moderate on-site Coulomb repulsion the intra-atomic Hund's interaction leads to the formation of nonzero ("bare") local moments on the Fe sites. We show that the Kondo-like exchange with the itinerant electrons may significantly renormalize the "bare" value of the moments manifested in different experiments. In turn, the itinerant carriers scatter on the renormalized moments that remain disordered in the paramagnetic phase. On the one hand, the scattering mechanism is responsible for high values of resistivity of the stoichiometric pnictides at the temperature of their transition into the antiferromagnetic phase, and on the other hand, it washes out the fine details of the Fermi surfaces. The results are rigorous and were obtained without use of any Born-type approximation. It also turned out that the value of the local moment and the inverse free time for scattering of carriers on the moments tend in the limit of the strong Kondo exchange to the finite universal values. The independence of the results on the on-site Coulomb repulsion is then illustrated in the frameworks of a simplistic model. It is shown that the spin density wave transition is driven by the Ruderman-Kittel-Kasuya-Yosida interactions between the renormalized moments via exchange by the electron-hole pairs. The applicability of the Boltzmann approach to transport in multiband pnictides is discussed briefly. DOI: 10.1103/PhysRevB.87.024504
- 出版日期2013-1-8
