Zn and Ni doping effects on Tc and spin gap behavior in YBa2Cu4O8 and YBa2Cu3O6.6

✍ Scribed by G.-q. Zheng; T. Odaguchi; Y. Kitaoka; K. Asayama; Y. Kodama; K. Mizuhashi; S. Uchida

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 249 KB
• Volume: 263
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(96)00083-4

✦ Synopsis

The existence of local moments in both Zn-and Ni-doped YBa2Cu408 (Y1248) is confirmed by a Curie-law T-dependence of NMR linewidth and the Cu relaxation at low T. The reduction of Cu-NQR signal intensity in Ni-doped Y1248 suggests that, in contrast to the case of Ni-doped YBa2Cu30 7 (Y1237), the Cu spin correlation around Ni is destroyed. This effect may be responsible for the larger reduction of T c by Ni-doping than in Y1237. For Cu sites which are away from an impurity by two lattice constants, I/T1T continues to increase below T*, at which it has a maximum in the non-doped material. The effect in reducing T*, which is sometimes called the spin gap temperature, is much more pronounced in Zn-doped samples, suggesting that the reduction of T * is mainly due to the induction of magnetic moments in the dx~y2 orbital, which may modify Cu spin fluctuation.