Ion-size effect on superconducting transition temperature Tc in R1−x−yPrxCayBa2Cu3O7−z systems (R=Er, Dy, Gd, Eu, Sm, and Nd)

Li-Chun Tung; J. C. Chen; M. K. Wu; Weiyan Guan

doi:10.1103/PhysRevB.59.4504

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Ion-size effect on superconducting transition temperature Tc in R1−x−yPrxCayBa2Cu3O7−z systems (R=Er, Dy, Gd, Eu, Sm, and Nd)

Li-Chun Tung, J. C. Chen, M. K. Wu, Weiyan Guan

DOI 10.1103/PhysRevB.59.4504 · Physical Review B

T1

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Abstract

We observed a rare-earth ion-size effect on Tc in R1−x−yPrxCayBa2Cu3O7−z (R=Er, Dy, Gd, Eu, Sm, and Nd) systems which is similar to that in R1−xPrxBa2Cu3O7−z systems in our previous reports. For fixed Pr and Ca concentration (fixed x and y), Tc is linearly dependent on rare-earth ion radius rR3+. For a fixed Pr concentration x, there exists a maximum of Tc (Tc,max) in Tc vs Ca concentration y curves. Tc,max shifts to higher Ca concentration region for samples with larger R ion radius. The enhancement of Tc (ΔTc,max=Tc,max−Tc,y=0; Tc,y=0 is the transition temperature Tc without Ca doping) increases with increasing R ion radius. We proposed an empirical formula for Tc (rR3+,x,y) to fit our experimental data: Tc(x,y)=Tc0−Aβ2(α/x+y/β)2−Bx. All fitting parameters in this formula, Tc0, B, β, α/β, and Aβ2, are rare-earth ion-size dependent.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Pr0.5Ca0.5Ba2Cu3O7-y Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
YBa2Cu3O6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
YBa2Cu3O7-y Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	90	Pressure not reported	unknown
Y1-xCaxBa2Cu3O7-y Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	90	Pressure not reported	unknown
Dy0.9-yPr0.1CayBa2Cu3O7-z Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	onset
Dy0.9-yPr0.1CayBa2Cu3O7-z Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	midpoint
Gd0.8-yPr0.2CayBa2Cu3O7-z Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Eu0.8-yPr0.2CayBa2Cu3O7-z Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	onset
Er0.8-yPr0.2CayBa2Cu3O7-z Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown