Magnetic and superconducting phase diagrams of single-crystal Er0.8R0.2Ni2B2C (R=Tb,Lu) and ErNi1.9Co0.1B2C: Identification of pair-breaking mechanisms

H. Takeya; M. El Massalami

doi:10.1103/PhysRevB.69.024509

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Magnetic and superconducting phase diagrams of single-crystal Er0.8R0.2Ni2B2C (R=Tb,Lu) and ErNi1.9Co0.1B2C: Identification of pair-breaking mechanisms

H. Takeya, M. El Massalami

DOI 10.1103/PhysRevB.69.024509 · Physical Review B

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Abstract

We investigated the magnetism, superconductivity and their interplay in single crystals Er0.8R0.2Ni2B2C (R=Tb,Lu) and ErNi1.9Co0.1B2C. In contrast to Co substitution, R substitutions induce considerable modifications in the magnetism of Er sublattice: e.g., Tb (Lu) substitution enhances (reduces) TN and critical fields. Both R substitutions introduce size effects and pinning centers; the former modifies the magnon specific heat while the latter hinders the formation of a weak ferromagnetism. The superconductivity, on the other hand, is strongly (weakly) influenced by Tb and Co (Lu) substitution. Taking LuNi2B2C as a nonmagnetic superconducting limit, we analyzed their superconductivities, as well as that of ErNi2B2C, in terms of multiple pair breaking theory on dirty superconductors. Based on this analysis, many of their superconducting features can be explained: The breakdown of de Gennes scaling is due to the presence of multiple pair breakers, the anisotropy of Hc2(T) is related to the magnetic anisotropy, the absence of a structure in Hc2(T) at TN of Lu substitution (TN<Tc) is attributed to an alloying-induced destruction of phase space truncation, and the quasi parabolic temperature dependence of Hc2(T) of Tb and Co substitutions is in part due to a saturation of antiferromagnetic correlations. For Lu substitution, the strength of magnon mediated pair breaking process(es) is substantially reduced.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
LuNi2B2C Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	16.5	Pressure not reported	unknown
ErNi2B2C Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	10.7	Pressure not reported	unknown
Er0.8Tb0.2Ni2B2C Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.7	Pressure not reported	unknown
Er0.8Lu0.2Ni2B2C Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	10.8	Pressure not reported	unknown
ErNi1.9Co0.1B2C Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.1	Pressure not reported	unknown