Search

Eu(Fe1−xRux)2As2 crystals were studied by resistivity and magnetization measurements. It is found that the SDW transition is gradually suppressed with the Ru doping and superconductivity with Tsc ~22 K emerges when x ≥0.2. The magnetic order of the Eu sublattice changes from A-type antiferromagnetic to ferromagnetic within x ≤0.2, making superconductivity and ferromagnetism coexist in a broad regime of 0.2 < x < 0.55.

Superconductivity (SC) and long-range ferromagnetism (FM) are mutually antagonistic, thus in general SC does not coexist with FM. In this mini-review, however, we will show that such a coexistence can inhabit several iron pnictide systems, including EuFe2(As1−xPx)2, Eu(Fe1−xCox)2As2, Eu(Fe1−xRux)2As2, CeFe(As1−xPx)O0.95F0.05 and Sr2VFeAsO3. We will briefly discuss the possible reasons and consequences of the coexistence of 3d-electron SC and 4f-electron FM.