Magnetoresistivity of thin films of the electron-doped high-TcsuperconductorNd1.85

Abstract

We report measurements of the magnetoresistance of Nd 1.85 Ce 0.15 CuO 4Ϯ␦ epitaxial thin films with varying oxygen content in magnetic fields H applied parallel (Hʈc͒ and perpendicular (HЌc͒ to the tetragonal c axis. We have observed critical scaling of the electrical resistivity that is consistent with a vortex-glass transition for a film with an optimum superconducting transition temperature T c of Ϸ22 K and Hʈc . The values of the zero-temperature upper critical field H c 2 (0)ϭ80 kOe and the in-plane zero-temperature coherence length ab (0)ϭ64 Å were obtained from an analysis of the fluctuation conductivity. For an overoxygenated film with T c Ϸ10 K, an anomaly develops with increasing field for Hʈc and TՇ2 K that is characterized by a minimum in the temperature dependence of the resistivity followed by a second resistive transition at a lower temperature, which is nearly independent of H. This behavior is similar to that previously observed in Nd 2Ϫx Ce x CuO 4Ϫ␦ single crystals and may be associated with the magnetic ordering of the Nd 3ϩ ions.

Doping dependence of normal- and superconducting-state transport properties ofNd2−xCexGollnik1, Naito2 1998Phys. Rev. B7112591View full textAdd to dashboardCite

“…43 For the n-type cuprates the upper critical field was determined from the fluctuation conductivity f luc . 44,45 Again, these values were larger than B * . In Ref.…”

Annealing effect on the electron-doped superconductorPr0.88LaCe0.12CuO4±δ

“…Actually, this regime was only noticed in some early works focusing on Nd 2−x Ce x CuO 4Ϯ␦ ͑NCCO͒ thin films. 4,5 Among the previous studies on the UA regime many experiments indicated that T c gradually increases to a saturated value with the oxygen removal, 7,8,25,26 and some recent works on PCCO thin films 8 and NCCO polycrystals 26 even suggested that the samples would be decomposed with further deoxygenated annealing. However, in this work, we demonstrate in the single crystals that this OA regime is really a bulk characteristic of electron-doped cuprates in which the sample is not decomposed while T c decreases with the oxygen removal.…”

“…While for electron-doped copper oxides such as RE 2−x Ce x CuO 4Ϯ␦ ͑RE =Pr,Nd,Sm,La͒ ͑RCCO͒, there is a long-standing issue that, besides doping carriers, annealing in a low-oxygen environment is necessary to induce superconductivity, 1,2 though the amount of the oxygen removed is extremely small, ␦ ϳ 0.01-0.04 ͑no more than 1%͒. 2 This oxygen-reduction annealing treatment drives the material continuously from an AF Mott insulator to a superconductor with very low normal-state resistivity, [3][4][5][6][7][8] accompanied by a sign change in Hall coefficient. 4,6,8 It was also suggested that oxygen-reduction process induces superconductivity by suppressing long-range AF order which seems to compete with superconducting order.…”

Pairing type change upon an increase in the cerium doping level in the Nd2 − x Ce x CuO4 + δ electronic superconductor

“…The mag netoresistance was studied for Nd 2 -x Ce x CuO 4 + δ epi taxial films with different oxygen concentrations; the slope of the upper critical field for optimally doped and optimally annealed sample was estimated as dH c2 /dT = -3.5 ± 0.3 kOe/K [15].…”