Anisotropic magnetic order of the Eu sublattice in single crystals of EuFe2−xCoxAs

Abstract

Here, we present a combination of magnetization and magnetic torque experiments to investigate the magnetic orders in undoped EuFe2As2 and Co doped EuFe1.8Co0.2As2 single crystals. Although at low temperatures typical results for an antiferromagnetic (AFM) state in EuFe2As2 were found, our data strongly indicate the occurrence of a canted antiferromagnetic (C-AFM) order of the Eu 2+ moments between 17 K and 19 K, observed even in the lowest studied magnetic fields. However, unlike in the parent compound, no low-field and low-temperature AFM state of the Eu 2+ moments was observed in the doped EuFe1.8Co0.2As2. Only a C-AFM phase is present at low fields and low temperatures, with a reduced magnetic anisotropy as compared to the undoped system. We present and discuss for both, EuFe2As2 and EuFe1.8Co0.2As2, the experimentally deduced magnetic phase diagrams of the magnetic ordering of the Eu 2+ sublattice with respect to the temperature, the applied magnetic field, and its orientation to the crystallographic axes. It is likely that the magnetic coupling of the Eu and the Fe sublattice is strongly depending on Co doping, having detrimental influence on the magnetic phase diagrams as determined in this work. Their impact on the occurrence of superconductivity with higher Co doping is discussed.

Phase diagram of Eu magnetic ordering in Sn-flux-grown Eu(Fe1−xCox)2AsJin1, Xiao2, Bukowski3 et al. 2016Phys. Rev. BSelf Cite302460View full textAdd to dashboardCite

“…41,42 On the other hand, the magnetic ground state of the Eu 2+ spins shows a systematic evolution with Co doping. Consistent with previous studies on Eu(Fe 1−x Co x ) 2 As 2 using Mössbauer spectroscopy and magnetic torque, 19,43 the magnetic ground state of the Eu 2+ moments is found to depend strongly on the Co doping level. For relatively low Co doping levels (the area in red), the ground-state magnetic structure of Eu is the Atype AFM structure (Fig.…”

The electronic phase diagrams of the Eu(Fe0.81Co0.19)2As2superconductor

“…3 et al [2] or a canting of the Eu 2+ moments from the c-axis was suggested by Guguchia et al [6] and Błachowski et al [7]. It is worth mentioning that Jiang et al [2], Niclas et al [4] and Guguchia et al [6] found a spin reorientation from an AF to a ferromagnetic (F) arrangement upon application of external magnetic fields or hydrostatic pressure.…”

“…3 et al [2] or a canting of the Eu 2+ moments from the c-axis was suggested by Guguchia et al [6] and Błachowski et al [7]. It is worth mentioning that Jiang et al [2], Niclas et al [4] and Guguchia et al [6] found a spin reorientation from an AF to a ferromagnetic (F) arrangement upon application of external magnetic fields or hydrostatic pressure. The only two reports of field-temperature H-T magnetic phase diagrams that we are aware of are those obtained for superconducting Eu(Fe 0.89 Co 0.11 ) 2 As 2 [2] and nonsuperconducting Eu(Fe 0.9 Co 0.1 ) 2 As 2 [6] crystals.…”

Pressure-induced ferromagnetism in antiferromagnetic Fe1.03Te

“…In comparison, an antiferromagnet can be easily tuned into a ferromagnet by application of a high magnetic field [26,27]. However, in this case not an itinerant antiferromagnetic spin density wave, but localized moments order ferromagnetically in these compounds.…”