The properties of the Y1−xPrxBa2Cu3O7 (YPrBCO) system are reviewed. These include superconducting, normal state, structural, chemical, optical, magnetic, and thermal properties. The destruction of superconductivity with Pr doping is discussed in view of possible models such as hole filling, localization, magnetic pair-breaking, and the role of hybridization. Applications to electronic devices using YBCO/PrBCO/YBCO multilayers are also reviewed.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400017489

A review of the superconducting and normal state properties of Y1−xPrxBa2Cu3O7

The crystal structure, superconductivity and magnetic properties of the title compounds have been investigated. The results revealed that with the concentration of Pr being constant, the transition temperatureTc of this system decreases with the increasing of La, or rather with the increasing of effective ionic radii of rare earth elements and the superconductivity disappears at aboutx=0.6. The coefficient of electron specific heat and the density statesN (0) which were infered from the magnetic measurements also decrease with the increasing of the effective radii. The relation between the radii of rare earth elements and hybridization is briefly discussed.

Superconductivity and magnetic properties in Pr0.2Yb0.8−xLaxBa2Cu3O7−δ

Among all the rare earth elements, Pr is known to behave as a singularity in the high-Tc families. When high-temperature cuprates are doped with Pr the superconductivity is quenched, and a metal insulator transition occurs. The origin of this behavior, being of fundamental interest, may also shed light on the mechanism of high-temperature superconductivity, since any reasonable theory for this mechanism should explain the behavior of the Pr-based system. The physical properties and the several theories which have been proposed to describe the anomalous behavior of Pr-doped systems in the normal and superconducting states are reviewed.

The question of Pr in HTSC

Magnetic properties of pelagic sediments from the western equatorial Pacific (Ocean Drilling Program (ODP) Site 805C) have been measured at low temperatures to investigate changes in magnetic mineralogy and the distribution of bacterial magnetite with depth. A saturation isothermal remanent magnetization (Mrs) was given to the samples by applying a strong magnetic field (2.5 T) at 20 K after cooling both in the absence (zero field cooling, ZFC) and presence of a 2.5 T magnetic field (field cooling, FC). The thermal demagnetization of both MrsZFC and MrsFC was measured from 20 to 300 K. No pronounced Verwey transition was observed in the data from samples shallower than the iron redox boundary. Below the boundary the Verwey transition is visible for all samples studied. We interpret this behavior as reflecting low-temperature oxidation (maghemitization) of primary magnetite and the subsequent dissolution of maghemite coatings below the iron redox boundary. The low-temperature oxidation may occur both at the water-sediment interface and deeper in the suboxic zone of sediments as a result of bacteria-mediated processes, including the reduction of nitrate compounds. MrsZFC and MrsFC thermal demagnetization curves of all samples diverge for the entire temperature range measured. The divergence may be caused by the low-temperature stabilization of spontaneous magnetization vectors along with exchange interaction in the magnetite maghemite system. Together, maghemitization and magnetic reduction diagenesis appear to play a dominant role in controlling the low-temperature properties of the sediment studied. As a result, low-temperature magnetic studies may provide more information on differences in reduction diagenesis than on the distribution of bacterial magnetite in natural sediments. The changes in effective oxidation state below the iron redox boundary detected by low-temperature methods may be useful in the study of some paleoenvironmental processes.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000JB900140

Low-temperature magnetic properties of pelagic sediments (Ocean Drilling Program Site 805C): Tracers of maghemitization and magnetic mineral reduction

The 90 K superconductor, YBa 2 Cu 3 O δ (YBCO), has proved to be highly adaptable chemically as it can accommodate a wide variety of cationic and anionic substitutions. Indeed, the majority of the chemical elements, excluding noble gases and actinides, have been reported to substitute to some extent into the YBCO structure. This review covers the literature on such substitutions and their effect on the properties of YBCO. Reported solubility limits are given, together with crystal symmetry and trends in unit cell parameters with dopant concentration. The dopant site is considered; this is additionally complex in the case of copper substitution because of the two distinct copper sites in the crystal structure. The effect of the dopant on the critical temperature, T c , is reviewed; the literature is often contradictory due to the dual effects of variable oxygen content and the nature of the dopant. Preparation methods appear to have an effect on solubility limits, crystal symmetry and T c , Also, the methods used to determine solubility limits are often imprecise which can lead to contradictions. The magnetic properties of doped materials are reviewed; for some dopants, particularly the magnetic lanthanides, antiferromagnetism and superconductivity co-exist. The related RBa 2 Cu 3 O δ phases (R = lanthanide), their structure, properties and behaviour on doping are reviewed in a similar way. For the larger rare earths, the related systems R 1+ x Ba 2- x CU 3 O δ , are reviewed; as x increases, the transition temperature decreases and compositions R 1.5 Ba 1.5 Cu 3 O δ are semiconducting. The upper and lower solubility limit changes with R, and for R = Dy, the upper limit is x = 0 composition, LaBa 2 Cu 3 O δ , cannot be prepared in air since substitution of La onto the Ba site occurs, forming the Ba-deficient solid solutions. The discovery of superconductivity above liquid nitrogen temperatures in YBa 2 Cu 3 O 7 , has generated a vast quantity of research; to date, > 20 000 papers have appeared on the 123 materials (source: BIDS). This review, therefore, cannot be comprehensive, but attempts to highlight important substitutions, their effect on the properties of YBCO and any contradictions in the literature.

Crystal chemical substitutions and doping of YBa2CU3Ox and related superconductors

The system Y{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3{minus}{ital y}}Fe{sub {ital y}}O{sub {ital z}}, with {ital x}=0 to 1, {ital y}=0 and 0.3, and {ital z}=6 and 7, has been studied by ac and dc magnetometry to determine the superconducting phase transition temperature, {ital T}{sub {ital c}}, by {sup 57}Fe Moessbauer spectroscopy to determine the antiferromagnetic phase transition temperature of the Cu(2) site, {ital T}{sub {ital N}}, and by specific-heat measurements to determine {gamma} and the antiferromagnetic ordering temperature of the Pr site, {ital T}{sub {ital n}}. {ital T}{sub {ital c}} ({ital x},{ital z}=7), {ital T}{sub {ital N}} ({ital x},{ital z}=6,7), and {ital T}{sub {ital n}} ({ital x},{ital z}=7) were obtained for {ital x} values of 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0. For {ital z}=6, {ital T}{sub {ital N}} changes very little with {ital x} ({ital T}{sub {ital N}}(0,6)=415 K and {ital T}{sub {ital N}}(1,6)=350 K), but for {ital z}=7, {ital T}{sub {ital N}} changes sharply with {ital x} ({ital T}{sub {ital N}}(1,7)=325 K, {ital T}{sub {ital N}}(0.6,7)=230 K, and {ital T}{sub {ital N}}(0.4,7){le}35 K). There is no conclusive evidence for overlap of superconductivity and antiferromagnetism. {ital T}{sub {ital n}} also decreases strongly with decreasing {ital x}, {ital T}{submore » {ital n}}(1,7)=17 K, while {ital T}{sub {ital n}}(0.4,7){le}2.5 K. The specific-heat measurements show large linear temperature terms. The slope {gamma} increases strongly with {ital x} and with the introduction of the Fe probe.« less

Magnetic order and superconductivity in Y1-xPrxBa2Cu3O7.

The antiferromagnetic (AFM) and superconducting (SC) phase-transition temperatures of ${\mathrm{Y}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3\mathrm{\ensuremath{-}}\mathit{y}}$${\mathit{M}}_{\mathit{y}}$${\mathrm{O}}_{\mathit{z}}$, M=Fe,Co,Zn, were studied by magnetometry and $^{57}\mathrm{Fe}$ M\"ossbauer spectroscopy For z\ensuremath{\sim}7, substitutions at all sites except those in the ${\mathrm{CuO}}_{2}$ planes (Pr,Fe,Co) cause superconductivity to disappear at ${\mathit{x}}_{\mathit{c}}$=05 or ${\mathit{y}}_{\mathit{c}}$=04 and antiferromagnetism to appear above ${\mathit{x}}_{\mathit{c}}$ and ${\mathit{y}}_{\mathit{c}}$ For z\ensuremath{\sim}6, antiferromagnetism persists for all x and y values On the other hand, substitution in the Cu(2) planes (Zn) suppresses both superconductivity at ${\mathit{y}}_{\mathit{c}}$=024 for z\ensuremath{\sim}7 and antiferromagnetism for z\ensuremath{\sim}6 No antiferromagnetism is seen for z\ensuremath{\sim}7

Competition between superconductivity and antiferromagnetism in Cu(2) layers of Y1-xPrxBa2Cu3-yMyOz, M=Fe,Co,Zn.

We report experimental data about the influence of Zn, Ga and Ni substitution of T c of the electron doped system Nd 1.85 Ce 0.15 Cu 1- y M y O 4- δ , 0≤ y ≤0.15. The relative suppression of T c for a given dopant concentration decreases from Ni to Ga to Zn. Superconductivity is totally suppressed above y =0.01, 0.03 and 0.05 for M= Ni, Ga, Zn, respectively. The solubility of M=Fe in the matrix is extremely small. The effect of M=Ga 3+ on T c is similar to that of Ce 4+ . We compare doping results for magnetic and nonmagnetic ions and discuss the origin of the depression of T c . The effect of these dopants on T c in the Nd-Ce-Cu-O system is completely diffrent from that observed in the La-Sr-Cu-O system.

Effect of Zn, Ga and Ni substitution on the superconducting properties of the electron doped system Nd-Ce-Cu-O

Angular dependence of the field-cooled, zero-field-cooled, and remanent magnetization in YBa2Cu3O7 single crystal.

In this article we try to elucidate the link between the morphological structure of YBa2Cu3O7−x (YBCO)‐silver composite sintered at 980 °C and the high flux pinning observed in this material. This YBCO/Ag system exhibits the suspension phenomenon in magnetic field gradient. The surface of the large YBCO grains is doped with silver and exhibits a high Tc=95 K. This doped phase shows a longer c axis than regular YBCO ceramic material. We believe that this high Tc phase forms a network of superconducting ‘‘rings’’ localized on the YBCO large grains. This network is probably the source of the high flux trapping phenomenon in the composite material.

U. Yaron

Papers

Magnetic order and superconductivity in Y1-xPrxBa2Cu3O7.

Competition between superconductivity and antiferromagnetism in Cu(2) layers of Y1-xPrxBa2Cu3-yMyOz, M=Fe,Co,Zn.

Effect of Zn, Ga and Ni substitution on the superconducting properties of the electron doped system Nd-Ce-Cu-O

Angular dependence of the field-cooled, zero-field-cooled, and remanent magnetization in YBa2Cu3O7 single crystal.

Magnetic suspension, critical current, and morphology in YBa2Cu3O7−x‐silver composites