Coexistence of ferromagnetism and superconductivity: magnetization and Mössbauer studies ofEuFe2(As1 − xPx)2

Abstract

Magnetization and 57Fe and 151Eu Mössbauerstudies of EuFe2(As1 − xPx)2 (x = 0–1.0) at temperatures (5–300 K) have been performed. The magnetization studies show adecrease of the divalent Eu sublattice antiferromagnetic transition temperature fromTAFM = 20 K forx = 0 to 16 Kat x≈0.2.For x > 0.2, the Eu sublattice is ferromagnetically ordered atTFM, which increases upto 27 K for x = 1.0. For0.2 < x < 0.5, the system becomessuperconducting. 151Eu Mössbauer studies in the antiferromagnetic range show a constant saturationhyperfine field of 26.2 T and that the magnetization is almost perpendicular to thec-axis. On the other hand, in the ferromagnetic range, the hyperfine field increases up to 30.8 T (forx = 1) and the easy axis is almost parallel to thec-axis. In both regions the magnetic axis seems to be tilted from the basal plane or thec-axisby ∼ 20°.The 57Fe Mössbauer studies show no magnetism in the iron site forx > 0.2, yet at 5 K exhibit transferred magnetic hyperfine fields (∼1 T) from the ferromagnetically ordered Eu sublattice, even in the superconducting region.Superconductivity in the presence of ferromagnetism is generally not observable. However,transferred magnetic hyperfine fields in the superconducting state are observed here for thefirst time.