Local and collective magnetism of EuFe2 As2

Abstract

We present an experimental study of the local and collective magnetism of EuFe2As2 that is isostructural with the high-temperature superconductor parent compound BaFe2As2. In contrast to BaFe2As2, where only Fe spins order, EuFe2As2 has an additional magnetic transition below 20 K due to the ordering of the Eu2+ spins (J=7/2, with L=0 and S=7/2) in an A-type antiferromagnetic texture (ferromagnetic layers stacked antiferromagnetically). This may potentially affect the FeAs layer and its local and correlated magnetism. FeKβ x-ray emission experiments on EuFe2As2 single crystals reveal a local magnetic moment of 1.3±0.15μB at 15 K that increases slightly to 1.45±0.15μB at 300 K. Resonant inelastic x-ray scattering experiments performed on the same crystals show dispersive broad (in energy) magnetic excitations along (0,0)→(1,0) and (0,0)→(1,1) with a bandwidth on the order of 170-180 meV. These results on local and collective magnetism are in line with other parent compounds of the AFe2As2 series (A=Ba, Ca, and Sr), especially the well-characterized BaFe2As2. Thus, our experiments lead us to the conclusion that the effect of the high magnetic moment of Eu on the magnitude of both the Fe local magnetic moment and spin excitations is small and confined to low-energy excitations.