Evidence for magnetic (AF SDW) 2D-phase transition in doped ferropnictides and ferroselenides

Abstract

The evidence for magnetic (AF SDW) 2D phase transition preceding a superconducting one (Tc < Tm) is presented for the plane of the FeAs(Se) layers of doped ferropnictides (-selenides). In contrast to the parent undoped compounds, the incommensurability of SDW and the lattice period leads to the formation of CDW with one-half wavelength. The magnetic phase (H-T) diagram of doped ferropnictides (-selenides) is characteristic of systems in which dielectric (e-h) and superconducting (e-e) pairings coexist.