Low Temperature Physics-LT 13 pp 605-609 | Cite as

# Direct Evidence for the Coexistence of Superconductivity and Ferromagnetism

## Abstract

In 1958 Matthias *et al*.^{1} proposed the simultaneous occurrence of superconductivity and ferromagnetism in certain substituted, cubic Laves-phase, intermetallic compounds. These compounds are generally of the type Ce_{1−x}R_{x}Ru_{2}, where R represents a magnetic rare earth. Their conclusion was based on the slow depression of the superconducting transition temperature *T* _{ c } *(x)* of CeRu_{2} upon addition of RRu_{2}, the depression of the ferromagnetic ordering temperature θ_{c}(*x*) of RRu_{2} upon addition of CeRu_{2}, and the intersection of*T* _{ c } *(x)* and θ_{ c } *(x)* at some finite temperature and rare earth concentration *x**. The phase diagram for the system Ce_{1−x }Gd_{x}Ru_{2} is shown in Fig. 1. Note that in the neighborhood of *x* = 0.13 the two critical curves intersect at about 4°K. The solid lines in Fig. 1 were obtained by low-field magnetic susceptibility measurements.^{2,3} The temperature at the midpoint of the transition to diamagnetism is taken as *T* _{ c }; below *T* _{ c } diamagnetic shielding masks any magnetic behavior of the sample. Values of θ*C* for the Gd-rich sample are determined from their paramagnetic behavior at higher *T*. The dashed lines are extrapolations assuming that the concentration dependences of *T* _{ c }(*x*) and θ_{ c }(*x*) persist above and below *x**, respectively. One therefore asks whether samples in the concentration region about *x** are either superconducting or ferromagnetic, or both, at temperatures below the dashed lines of Fig. 1. *T* _{ c } transitions have been observed^{1,4} for certain systems with magnetic rare earth concentrations slightly above their *x**. Recently θ*C* values below *T* _{ c } for *x* < *x** were inferred^{3} from susceptibility data taken above *T* ^{ c }.

## Keywords

Magnetic Order Magnetic Hyperfine Field Magnetic Hyperfine Rare Earth Concentration Magnetic Rare Earth## Preview

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## References

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