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.

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

A field effect transistor fabricated with an oxide channel has been shown to demonstrate switching characteristics similar to conventional silicon metal oxide field effect transistors. This device is believed to operate via a Mott metal-insulator transition induced by the gate field, and offers a potential technology alternative for the regime beyond silicon scaling limitations.

Mott transition field effect transistor

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

The crystallographic changes that occur with increasing Pr concentration in the Y−xPrxBa2Cu3O7−δ system have been studied by neutron diffraction. As x is increased from 0 to 1, the orthorhombic a, b and c lattice parameters expand monotonically, while the orthorhombic distortion, espressed as b a , decreases, reflecting increased occupation of O(5) sites at the expense of O(4) chain site occupancy. The separation of the CuO2 planes in PrBa2Cu3O7−δ indicates that the Pr ions have an intermediate valence of ∼3.3 in this compound. Evidence is presented for increased interaction between the Pr ions and oxygen ions in adjacent CuO2 planes.

Neutron diffraction study of Pr valence and oxygen ordering in the Y1−xPrxBa2Cu3O7−δ system

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

Substitution of Pr for Y in the Y{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} system depresses {ital T}{sub {ital c}}, with superconductivity disappearing for {ital x}{ge}0.5. The origin of this {ital T}{sub {ital c}} depression is still controversial, as is the valence state of the Pr ion. In order to study these problems, single-phase materials were prepared with {ital x}=0.0, 0.1, 0.2, 0.3, 0.35, 0.4 0.45, 0.5, 0.6, 0.7, 0.9, and 1.0. Under certain annealing conditions, these types of samples will phase separate into YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} and Y{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}, showing two transitions in the magnetization, but will still appear single phase from x-ray diffraction. We have overcome this problem through specific annealing conditions of time, temperature, and atmosphere. We find that the superconductivity is strongly suppressed as a function of Pr concentration, with a behavior which is consistent with the classical Abrikosov-Gor'kov pair-breaking theory. The critical fields versus {ital T} show a bell''-shaped behavior, which is consistent with the presence of magnetic pair-breaking interactions. The measured temperature dependence of the critical field, {ital H}{sub {ital c}2} near {ital T}{sub {ital c}}, and the Pauli susceptibility, are used to estimate the physicalmore » parameters {lambda}{sub GL}, {xi}{sub GL}, and {gamma}.« less

Upper critical field and normal-state properties of single-phase Y1-xPrxBa2Cu3O7- gamma compounds.

Samples of LaBaCaCu/sub 3/O/sub 7+//sub delta/ were prepared by standard solid-state reactions. X-ray powder diffraction data taken in the temperature range 6--300 K reveal no structural transition. Thermogravimetric analysis was used to determine the oxygen content delta. Both magnetization and resistivity measurements indicate sharp superconducting transitions (..delta..T 0) achieved by high-pressure oxygen annealing showed a broad transition, as well as a T/sub c/ which was depressed by 10 K. We consider these experimental results in the context of ordering of the cations La, Ba, and Ca as well as oxygen sublattice ordering. We estimate the electronic coefficient of specific heat ..gamma.. and the Ginzburg-Landau parameters xi/sub GL/, lambda/sub GL/, and kappa/sub GL/ from the measured temperature dependence of H/sub c//sub 2/ and the Pauli susceptibility.

Preparation, characterization, and superconducting properties of tetragonal LaBaCaCu3O7+ delta.

Low-temperature (260 {degree}C) and short-time ({gt}5-min) treatment of initially insulating YBa{sub 2}Cu{sub 3}O{sub 62} with Br{sub 2} gas converts the material into a 90-K superconductor Bromine diffusion is found to be four orders of magnitude greater than oxygen diffusion at the same temperature The crystal structure, phase purity, microstructure, thermal stability, and oxygen content have been studied using x-ray-diffraction Rietveld analysis, Raman spectroscopy, x-ray-fluorescence microprobe, and thermal gravimetric analysis Superconducting and normal-state properties of the brominated material have been studied with diffuse infrared reflectivity and magnetization

Metallization and superconducting properties of YBa2Cu3O6.2Bry.

The upper critical fields, H c2 , for Y 1−x Pr x Ba 2 Cu 3 O 7 are observed to be “bell” shaped for x ≥ 0.3. This provides strong evidence for the importance of magnetic interactions in this system.

P.A. Hahn

Papers

Upper critical field and normal-state properties of single-phase Y1-xPrxBa2Cu3O7- gamma compounds.

Preparation, characterization, and superconducting properties of tetragonal LaBaCaCu3O7+ delta.

Metallization and superconducting properties of YBa2Cu3O6.2Bry.

Magnetic pair breaking in Y1−xPrxBa2Su3O7