Interplay of 4f and 3d moments in EuFe2As2 iron pnictides

EuFe2As2 is unique among 122 iron pnictides due to its 4f magnetic moments. We review its properties with particular emphasis on the interplay between 4f and 3d moments. After discussing the parent compound, we first focus on the evolution of magnetism and superconductivity for hole-doped Eu1-xKxFe2As2 as well as for chemical and hydrostatic pressure in EuFe2(As1-xPx)(2) . Non-Fermi liquid behavior for optimally doped superconducting systems is highlighted in the electrical resistivity and thermoelectric power. We also discuss the in-plane anisotropy and how the indirect magnetoelastic coupling between Eu 4f moments and the crystal structure can be used for persistent detwinning of EuFe2As2 in the orthorhombic state by small magnetic fields. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim