Effect Eu2+ on the magnetism of the FeAs layer and in the onset of superconductivity in EuFe2As2

EuFe2As2 is an interesting compound of the 122 series because of the coexistence of superconductivity and ferromagnetism originating from Eu2+ that has spin-only magnetic moment of 7µB. In normal state EuFe2As2 exhibits two magnetic transitions. The first one at ≈190 K concerns the AF ordering of the spins at the Fe sites, while the second one is observed at ≈20 K and involves the ordering of spins on Eu2+. The spins of Eu order in an A-type antiferromagnetic (AF) ordering (the ordering is AF between different layers but ferromagnetic inside a single Eu plane). This additional magnetic phase and the constant presence of high magnetic moment on the spacing layer do not preclude the emergence of superconductivity (SC) when doping is performed, representing one of the few cases in which ferromagnetism and SC are close in the phase diagram of Fe pnictides. This leads to the natural question of whether the high magnetic moment of Eu2+ affects the magnetism of the FeAs layer.