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Phase diagram of Eu(Fe1-xCox)2As2 single crystals


Superconductivity can be achieved in EuFe2As2 system by chemical substitution of Fe with Co. By complementary macroscopic and neutron diffrac­tion measurements on a series of Sn-flux grown single crys­tals with different Co-doping levels, we were able to construct a specific phase diagram of Eu(Fe1-xCox)2As2. Both the structural phase transition and the SDW transition of Fe are continuous­ly suppressed by Co-doping. The magnetic ground state of the Eu2+moments depends strongly on the doping level of Co, developing from the A-type antiferromagnetic (AFM) order in the parent compound, via the A-type canted AFM structure at intermediate Co doping levels, finally to the pure FM order at relatively high Co doping levels. 

The doping-induced modification of the indirect Ru­derman-Kittel-Kasuya-Yosida (RKKY) interaction between the Eu2+moments is believed to be responsible for the change in the magnetic ground state of Eu. In addition, for Eu(Fe1-xCox)2As2with 0.10 ≤ x ≤ 0.18, strong ferromagnetism from the Eu sublattice is well devel­oped in the superconducting state.

W. T. Jin et al., “Phase diagram of Eu magnetic ordering in Sn-flux-grown Eu(Fe1-xCox)2As2 single crystals”, Phys. Rev. B 94, 184513 (2016).

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