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Author (up) Ghamaty, S.; Lee, B. W.; Neumeier, J. J.; Nieva, G.; Maple, M. B.
Title Low-temperature specific heat of the Y1-xPrxBa2Cu3O7-δ system Type Journal Article
Year 1991 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 43 Issue Pages 5430
Keywords
Abstract Low-temperature specific-heat C measurements as a function of temperature T between 0.5 and 30 K are reported for Y1-xPrxBa2Cu3O7-δ compounds with x=0, 0.2, 0.3, 0.4, 0.6, 0.8, and 1.0. The Pr contribution to the specific heat of all of the samples can be described as the sum of a Pr nuclear Schottky anomaly of the form CN(T)=AT-2, a linear term CL(T)=γT, and a Pr magnetic anomaly. For compounds with x≤0.6, which are metallic and superconducting, the Pr magnetic specific-heat anomaly has the same temperature dependence as a Kondo anomaly. For the compounds with x≥0.8, which are insulating, the magnetic specific-heat anomaly is consistent with antiferromagnetic ordering of the Pr ions with Néel temperatures TN of 10.9 and 15.7 K for x=0.8 and 1.0, respectively. For T<TN, the antiferromagnetic specific-heat anomaly has the form CM(T)=MT3, characteristic of three-dimensional antiferromagnetic magnons.
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Call Number BT @ gnieva @ Serial 437
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Author (up) Nieva, G.; Lee, B. W.; Guimpel, J.; Iwasaki, H.; Maple, M. B.; Schuller, I.K.
Title Changes in the Pr-induced TC depression of 123 compounds by chemical pressure Type Journal Article
Year 1991 Publication Physica C: Superconductivity Abbreviated Journal Physica C
Volume 185-189 Issue 1 Pages 561-562
Keywords
Abstract We present structural data refined from X-ray spectra for R1−xPrxBa2Cu3O7−δ (R=Er, Gd, Eu, Sm, Nd) systems with x=0, 0.1, and 0.4. The evolution of Tc with the ionic radius of the rare earth for different values of x can be related to the Cu2---O4 distance. The effect of chemical pressure on Tc in R1−xPrxBa2Cu3O7−δ systems is opp osite to that of hydrostatic pressure on the Y1−xPrxBa2Cu3O7−δ system.
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Notes Approved no
Call Number BT @ gnieva @ Serial 439
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Author (up) Nieva, G.; Ghamaty, S.; Lee, B. W.; Maple, M. B.; Schuller, I.K.
Title Superconductivity and magnetism in Eu1-xPrxBa2Cu3O7-δ Type Journal Article
Year 1991 Publication Physical Review B Abbreviated Journal Phys. Rev. B
Volume 44 Issue Pages 6999
Keywords
Abstract Measurements of the electrical resistivity ρ as a function of temperature T, and low-temperature specific heat C as a function of T and magnetic field H, have been performed for Pr concentrations 0≤x≤1 in the Eu1-xPrxBa2Cu3O7-δ system (δ≊0.05). The superconducting critical temperature Tc(x) in the metallic phase (0≤x≲xc≊0.5) was determined from the resistivity ρ(x,T), while the Néel temperature TN(x) in the insulating phase (xc≲x≤1) was inferred from specific-heat anomalies due to antiferromagnetic (AFM) ordering of the Pr ions. The effect of ‘‘chemical’’ pressure on Tc(x) in the Y1-xPrxBa2Cu3O7-δ system is opposite to that of applied hydrostatic pressure. The Pr contributions to the specific heat in the insulating phase have the form C(T)=MT3 for T<TN, characteristic of three-dimensional AFM magnons. In contrast, the Pr contribution to C(T) in the metallic phase takes the form of a broad anomaly that can be described by a spin-1/2 Kondo model. The entropy associated with the Pr specific-heat anomalies in both the metallic and insulating phases is close to R ln2, indicative of a doublet ground state for Pr in the crystalline electric field and a Pr valence close to 4+.
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Publisher Place of Publication Editor
Language Summary Language Original Title
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Area Expedition Conference
Notes Approved no
Call Number BT @ gnieva @ Serial 438
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