Stewardship - PR Star of Library Advancement

Stewardship, a close relative of donor/prospect cultivation, is the ongoing appreciation and provision of information to benefactors and a critical element in institutional advancement. But stewardship is more than appreciation and information. For it to be as effective as possible for library advancement, it must be packaged as public relations at its best. As Robert Wedgeworth indicates throughout his article entitled “Donor Relations as Public Relations...,” there is an inextricable link between stewardship and public relations. At the University Libraries of Notre Dame, we recognized this some years ago and began to take measured steps toward a comprehensive stewardship package. Our journey is not complete, nor has it been perfectly executed. But our progress has been good and largely effective, and we are vigilant in honing the former and eliminating the obstacles to the latter

Comment on ``Superconducting PrBa_2Cu_3O_x''

Recently, Zou et al. (Phys. Rev. Lett. 80, 1074, 1998) reported the observation of bulk superconductivity (SC) for a PrBa_2Cu_3O_x (Pr123) single crystal grown by the traveling-solvent floating zone (TSFZ) method. The aim of this Comment is to show the inconsistency of the value of effective magnetic moment \mu_{eff} reported by Zou et al. (2.92\mu_B) with their magnetic susceptibility data. The estimation made directly from their data points gives a considerably smaller value of \mu_{eff}=2.09\mu_B. At the same time the values of mu_{eff}=2.9\mu_B and 3.1\mu_B were obtained for our Pr123 single crystals grown by flux method for H||ab-plane and H||c-axis, respectively. This suggests that Pr occupies only about a half of the RE sites in TSFZ crystal. The other half of the RE sites is occupied most probably by the nonmagnetic Ba. Noteworthy, SC with T_c=43 K was observed earlier for Pr_{0.5}Ca_{0.5}Ba_2Cu_3O_{7-y} thin films. Ba^{2+} has a larger ionic radius than Pr^{3+} and so the substitution of Ba for Pr could give a natural explanation not only for the SC in TSFZ Pr123 but also for the elongation of the distance between the CuO_2 planes observed by Zou et al.Comment: Slightly extended version of Comment accepted to Phys. Rev. Lett. (v.81, N24, 1998), tentatevely to be publ. 14Dec98. 1 page, REVTex; 1 EPS fi

Magnetically ordered Cu and Ru in Ba2GdRu1-uCuuO6 and in Sr2YRu1-uCuuO6

[[abstract]]Magnetic orderings of the Cu, Gd, and Ru moments in nonsuperconducting Ba2GdRu1-uCuuO6 and of the Cu and Ru moments in superconducting Sr2YRu1-uCuuO6 (whose superconducting onset temperature is ~45 K) have been studied using dc susceptibility, microwave magnetic resonance, and neutron diffraction (on Sr2YRu0.85Cu0.15O6 only). In both homologues, Cu exhibits antiferromagnetism with an ordering temperature of ~86 K (much greater than the resistive superconductivity onset transition of ~45 K), and a magnon energy gap ħωmagnon (q=0) that exceeds the microwave photon frequency of ω/2π=13 GHz. The Cu moment extracted from neutron data for Sr2YRu1-uCuuO6 is ~1.7μB at low temperature. Gd, in Ba2GdRu1-uCuuO6, is paramagnetic and displays a g=2 electron spin resonance at temperatures above ~48 K, which also persists well below ~48 K (but with a very much broadened line), and orders antiferromagnetically at ~12 K. Ru in Ba2GdRu1-uCuuO6 orders at ~48 K, but in Sr2YRu1-uCuuO6 orders at ~23 K and has a moment of ~1.6μB, extracted from neutron scattering data. In both Sr2YRu1-uCuuO6 and Ba2GdRu1-uCuuO6 the Ru orders ferromagnetically in the a-b planes with the sheet magnetization alternating in direction as one moves along the c axis, forming a net antiferromagnetic structure. We find no evidence of a Ru signature in the magnetic resonance data anywhere in the range from 3 to 300 K, a result which is consistent with the electrons being itinerant. Attempts to detect Ru magnetic resonances in various other materials have also failed. Since in Sr2YRu1-uCuuO6 the magnetic moments of the Ru and the Cu are ordered at low temperatures, its superconductivity is inconsistent with a spin-fluctuation pairing model.[[incitationindex]]SCI[[booktype]]紙

Anomalous Magnetic Ordering in PrBa₂Cu₄O₈ and CmBa₂Cu₃O₇

A review of temperature-dependent magnetization data for nonsuperconducting PrBa2Cu4O8 and CmBa2Cu3O7 suggests that the failure of each to superconduct is related to the presence of Pr and Cm on their respective Ba sites. This defect is manifested, in each case, by short c-axis lattice parameters and anomalous high-temperature magnetic ordering which has been incorrectly attributed to ordering of the entire magnetic sublattice. Instead, it is shown that the anomalous high-temperature ordering as seen in the magnetization data is consistent with the ordering of magnetic ions substituted on the Ba site

Studies on La2-xPrxCayBa2Cu4+yOz (0.1 < x < 0.5) type mixed oxide superconductors

The La2-xPrxCayBa2Cu4+yOz (LaPrCaBCO) mixed oxides have been studied for their structural and superconducting properties using X-ray diffraction (XRD), d. c. resistivity, d. c. susceptibility and iodometric double titration. All the LaPrCaBCO samples for x = 0.1 - 0.5, exhibit tetragonal crystalline structure with P 4/mmm space group as determined by Rietveld analysis of the X-ray diffraction data. With increasing x, enhancement in Tc is observed, which is quite interesting for Pr substituted high Tc oxides. Maximum Tc ~ 58 K has been observed for x = 0.5(La-2125 stoichiometry). The results of structural studies and superconducting property measurements are presented in light of increase in Tc in LaPrCaBCO system with increasing Pr concentration.Comment: 6 pages including 5 figures and 1 tabl

On the possibility of superconductivity in PrBa2Cu3O7

Recent reports about observations of superconductivity in PrBa2Cu3O7 raise a number of questions: (i) of various theories striving to explain the Tc suppression in PrxY{1-x}Ba2Cu3O7, are there any compatible with possible superconductivity in stoichiometric PrBa2Cu3O7? (ii) if this superconductivity is not an experimental artifact, are the superconducting carriers (holes) of the same character as in the other high-Tc cuprates, or do they represent another electronic subsystem? (iii) is the underlying mechanism the same as in other high-Tc superconductors? I present an answer to the first two questions, while leaving the last one open.Comment: 4 pages 4 eps fig

Anomalous magnetic ordering in PrBa_2Cu_3O_{7-y} single crystals: Evidence for magnetic coupling between the Cu and Pr sublattices

In Al-free PrBa_2Cu_3O_{7-y} single crystals the kink in the temperature dependence of magnetic susceptibility chi_{ab}(T), connected with Pr antiferromagnetic ordering, disappears after field cooling (FC) in a field H || ab-plane. The kink in chi_c(T) remains unchanged after FC in H || c-axis. As a possible explanation, freezing of the Cu magnetic moments, lying in the ab-plane, caused by FC in H || ab, hinders their reorientation and, due to coupling between the Pr and Cu(2) sublattices, ordering of the Pr^{3+} moments. A field induced phase transition and a field dependence of the Pr^{3+} ordering temperature have been found for both H || c and H || ab.Comment: 11 pages (LaTex with elsart.sty), 5 EPS figs. Accepted to Physica

The Decomposition of YBa₂Cu₃O₇₋δ Doped into Ba₂YRuO₆

One of the persistent criticisms of claims for observation of superconductivity in Ba2YRu1−uCuuO6 (O6) is that the diamagnetism is actually due to the decomposition of the material into YBa2Cu3O7−delta and other phases. We report a series of experiments in which YBa2Cu3O7−delta is doped into Ba2YRuO6 and carried through a series of sintering steps which were followed by magnetization, neutron diffraction, and scanning electron microscopy/microprobe measurements. It was found that the dopant YBa2Cu3O7−delta decomposed and failed to reform with cooling. It is concluded that the O6 phase is the stable high-temperature phase. The Cu released from the Y123 decomposition doped the host Ba2YRuO6, in partial substitution for Ru. This doping resulted in a small diamagnetic response with an onset temperature of ~84 K

Origin of the Superconductivity in the Y-Sr-Ru-O and Y-Sr-Cu-O Systems

We report on the structural, magnetic, and Raman-scattering studies of double perovskite structure Sr2Y(Ru1-xCux)O6-d systems made by systematic synthesis processes with various numbers of doping concentrations and sintering temperatures. We observed different behaviors resulting from the different thermal treatments. In particular, superconductivity in Cu-doped Sr2YRuO6 has been observed only for partially melted ceramic materials. We show that superconductivity is associated with the 1:2:3 phase (YSr2Cu3Ot), similar to that of Y-Sr-Cu-O samples sintered at high temperature

Electronic and Magnetic Properties of Electron-doped Superconductor, Sm_{1.85}Ce_{0.15}CuO_{4-delta}

Temperature-dependent magnetization (M(T)) and specific heat (C_p(T)) measurements were carried out on single crystal Sm_{1.85}Ce_{0.15}CuO_{4-delta} (T_c = 16.5 K). The magnetic anisotropy in the static susceptibility, chi {equiv} M/H, is apparent not only in its magnitude but also in its temperature dependence, with chi_{perp} for H{perp}c larger than chi_{parallel} for H{parallel}c. For both field orientations, chi does not follow the Curie-Weiss behavior due to the small energy gap of the J = 7/2 multiplet above the J = 5/2 ground-state multiplet. However, with increasing temperature, chi_{parallel}(T) exhibits a broad minimum near 100 K and then a slow increase while chi_{perp}(T) shows a monotonic decrease. A sharp peak in C_p(T) at 4.7 K manifests an antiferromagnetic ordering. The electronic contribution, gamma, to C_p(T) is estimated to be gamma = 103.2 (7) mJ/moleSmK^2. The entropy associated with the magnetic ordering is much smaller than Rln2, where R is the gas constant, which is usually expected for the doublet ground state of Sm^{+3}. The unusual magnetic and electronic properties evident in M(T) and C_p(T) are probably due to a strong anisotropic interaction between conduction electrons and localized electrons at Sm^{+3} sites.Comment: 5 pages, 5 encapsulated postscript figures, late