Magnetism and superconductivity in single crystals $Eu_{1-x}Sr_xFe_{2-y}Co_{y}As_2$

Q. J. Zheng; Y. He; T. Wu; G. Wu; H. Chen; J. J. Ying; R. H. Liu; X. F. Wang; Y. L. Xie; Y. J. Yan; Q. J. Li; X. H. Chen

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arXiv · 0907.5547

Magnetism and superconductivity in single crystals $Eu_{1-x}Sr_xFe_{2-y}Co_{y}As_2$

Q. J. Zheng·Y. He·T. Wu·G. Wu·H. Chen·J. J. Ying·R. H. Liu·X. F. Wang·Y. L. Xie·Y. J. Yan·Q. J. Li·X. H. Chen

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Abstract

We systematically studied the transport properties of single crystals of $Eu_{1-x}Sr_xFe_{2-y}$Co$_{y}As_2$. 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 $Eu^{2+}$ 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 $Eu^{2+}$ spins is induced by magnetic field. Superconductivity without resistivity reentrance shows up by partial substitution of Eu$^{2+}$ with non-magnetic Sr$^{2+}$ to completely destroy the AFM ordering of $Eu^{2+}$ spins. These results suggest that the antiferromagnetism destroys the superconductivity, while the ferromagnetism can coexist with the superconductivity in the iron-based high-$T_c$ superconductors.

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Q. J. Zheng, Y. He, T. Wu, G. Wu, H. Chen, J. J. Ying, R. H. Liu, X. F. Wang, Y. L. Xie, Y. J. Yan, Q. J. Li, X. H. Chen. 2009-07-31. Magnetism and superconductivity in single crystals $Eu_{1-x}Sr_xFe_{2-y}Co_{y}As_2$. https://arxiv.org/abs/0907.5547

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