ScienceAsia 24 (1998): 133-139 |doi: 10.2306/scienceasia1513-1874.1998.24.133

ON THE DEPRESSION OF T_c OF REBa₂Cu₃O_7- (RE = Y, Er) DUE TO NI²⁺ SUBSTITUTION INTO THE Cu(2) SITES. (s+d)-WAVE MODEL INTERPRETATION

K. KONGSAKULYANON^a, W. TANGTATHARAKUL^a AND I.M. TANG^b

ABSTRACT: The depressions of the T_c’s of two c123e. REBa₂Cu₃O₇ ( Re = Y, Er ) HTSC's due to magnetic ( Ni²⁺ ) transition metal substitution into the Cu(2) layer are studied. Special attention is paid to the difference in the orthorhombicity ( D = (b-a)/a, where a and b are the lattice parameters in the basal plane) of the two superconductors. It is observed that the rate of depression dT_c/dx for the cY-123e. HTSC is slightly steeper than that for the cEr-123e. HTSC. The difference in the rates of depression is explained in terms of a connection between the orthorhombicity and the superconducting state. It is assumed that the orthorhombic distortion induces a change in the pairing interaction. The modification of the pairing interaction leads to a new superconducting state in which order parameter (OP) has (s + d)-wave symmetry

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a Department of Physics, Faculty of Science & Technology, Rangsit Campus Thammasat University, Patum Thani 12121, Thailand.
b Department of Physics, Faculty of Science Mahidol University, Bangkok 10400, Thailand.

Received May 3, 1998