Spin Correlation in High-<i>T</i>_cCuprate HgBa₂Ca₂Cu₃O_8+δwith<i>T</i>_c=133 K –An Origin of<i>T</i>_c-Enhancement Evidenced by⁶³Cu-NMR Study–

Abstract

The Knight shift, the nuclear spin-lattice relaxation rate, 1/ T 1 , and the transverse relaxation rate, 1/ T 2G , of 63 Cu have been separately measured for the square and the pyramidal CuO 2 planes in HgBa 2 Ca 2 Cu 3 O 8+δ (Hg1223) with the highest transition temperature, T c =133 K to date. From the quantitative analysis of 1/ T 1 and 1/ T 2G , it is shown that the product of the staggered susceptibility and the characteristic energy of spin fluctuations around a zone boundary, χ Q Γ Q , for the square CuO 2 plane site is larger than that for YBa 2 Cu 3 O 7 (YBCO 7 ), although that for the pyramidal CuO 2 plane site is almost the same. This enhancement of χ Q Γ Q for the square site is considered to be responsible for the higher T c in Hg1223 than in YBCO 7 .