Magnetism and superconductivity in single crystals Eu₁₋ₓSrₓFe₂₋yCoyAs₂

الأصل · EN

We systematically studied the transport properties of single crystals of Eu₁₋ₓSrₓFe₂₋yCoyAs₂. Co doping can suppress the spin-density wave (SDW) ordering and induces a superconducting transition, but a resistivity reentrance due to the antiferromagnetic ordering of Eu²⁺ spins is observed, indicating the competition between antiferromagnetism (AFM) and superconductivity. It is striking that the resistivity reentrance can be completely suppressed by external magnetic field (H) because a metamagnetic transition from antiferromagnetism to ferromagnetism for Eu²⁺ spins is induced by magnetic field. Superconductivity without resistivity reentrance shows up by partial substitution of Eu²⁺ with non-magnetic Sr²⁺ to completely destroy the AFM ordering of Eu²⁺ spins. These results suggest that the antiferromagnetism destroys the superconductivity, while the ferromagnetism can coexist with the superconductivity in the iron-based high-Tc superconductors.