Periodicity Change in Structural Modulation in Bi₂Sr₂Ca_1-yRE_yCu₂O_8+δ (RE=Y, Nd) System

Abstract

Changes in structural modulation for the Bi 2 Sr 2 Ca 1- y RE y Cu 2 O 8+δ system (RE=Y, Nd), accompanied with the transition from the superconductor to the antiferromagnetic insulator, were examined. In the Bi 2 Sr 2 Ca 1- y Y y Cu 2 O 8+δ system, the modulation periodicity continuously decreased, from about 5.0 times to 4.0 times the length of the subcell along the b axis, with increasing Y content substituted. The modulation periodicity for Bi 2 Sr 2 NdCu 2 O 8+δ was about 4.0 times the length of the subcell along the b axis, the same as in the Bi 2 Sr 2 YCu 2 O 8+δ . This decrease in the modulation periodicity is attributed to the valence change of Y 3+ for Ca 2+ .