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Substitution of Nd at Ba site in Gd123
Author(s) -
Mirzadeh M.,
Akhavan M.
Publication year - 2006
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200541372
Subject(s) - electrical resistivity and conductivity , condensed matter physics , superconductivity , orthorhombic crystal system , tetragonal crystal system , materials science , variable range hopping , doping , ferromagnetism , flux pinning , analytical chemistry (journal) , crystallography , chemistry , high temperature superconductivity , crystal structure , physics , chromatography , quantum mechanics
Structural and superconducting behaviors of Gd(Ba 2− x Nd x )Cu 3 O 7+ δ with 0.0 ≤ x ≤ 0.8 have been studied by X‐ray diffraction and electrical and magnetic measurements. The XRD patterns show the samples with x ≤ 0.5 are isostructure 123 phase, and an orthorhombic–tetragonal phase transition occurs at x = 0.2. The transition temperature decreases linearly with increasing Nd content. This behavior is also observed in the curves of the room‐temperature resistivity versus Nd doping. The metal–insulator and superconductor–insulator transitions occur at x c MIT = 0.3 and x c SIT = 0.35, respectively. The conduction mechanisms of the normal‐state resistivity are the Coulomb gap (CG) for x < x c MIT , two‐dimensional variable‐range hopping (2D‐VRH) at x c MIT ≤ x ≤ x c SIT , and 3D‐VRH for x > x c SIT . The pinning energy derived from the thermally activated flux creep model, and coupling energy derived from the Ambegaokar–Halperin theory decrease with increasing applied magnetic field as a power‐law relation, and decrease as Nd content increases. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)