Anisotropic magnetic order of the Eu sublattice in single crystals of

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 Eu2+ moments between 17 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 Eu2+ 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 discuss for both EuFe2As2 and EuFe1.8Co0.2As2 the experimentally deduced magnetic phase diagrams of the magnetic ordering of the Eu2+ 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 dependent 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. DOI: https://doi.org/10.1103/PhysRevB.84.144506 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-50935 Accepted Version Originally published at: Guguchia, Z; Bosma, S; Weyeneth, S; Shengelaya, A; Puzniak, R; Bukowski, Z; Karpinski, J; Keller, H (2011). Anisotropic magnetic order of the Eu sublattice in single crystals of EuFe2xCoxAs2(x = 0, 0.2)studiedbymeansofmagnetizationandmagnetictorque.PhysicalReview.B, CondensedMatterandMaterialsPhysics, 84(14) : 144506. DOI: https://doi.org/10.1103/PhysRevB.84.144506 Study of the anisotropic magnetic order of the Eu sublattice in single crystals of EuFe2−xCoxAs2 (x=0, 0.2) by means of magnetization and magnetic torque Z. Guguchia,∗ S. Bosma, and S. Weyeneth Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland