Slow transverse relaxation of the Zn-neighbor Cu nuclear spins in YBa2(Cu{1-x}Znx)4O8

TL;DR

This paper explains why Cu nuclear spins near Zn impurities in YBa2(Cu{1-x}Znx)4O8 have longer spin-spin relaxation times, attributing it to distant coupling effects rather than a lack of local spin susceptibility enhancement.

Contribution

It provides a theoretical explanation for the observed long T_{2G} of Zn-neighbor Cu nuclear spins in heavily Zn-substituted YBa2(Cu{1-x}Znx)4O8.

Findings

Longer T_{2G} due to distant nuclear spin coupling near Zn

Distant coupling does not imply absence of local spin susceptibility enhancement

Theoretical insight into nuclear spin relaxation behavior in Zn-substituted cuprates

Abstract

An explanation is given for the recent observation in the plane-site Cu nuclear quadrupole resonance (NQR) study of a heavily Zn-substituted YBa$_2$(Cu$_{1-x}$Zn$_x$)$_4$O$_{8}$ that the Cu nuclear spin-spin relaxation time $T_{2G}$ near the impurity Zn is longer than that away from Zn. The long $T_{2G}$ of the Zn-neighbor Cu nuclear spins results from a distant coupling between only a few nuclear spins near Zn, which does not indicate the absence of local enhancement of the staggered spin susceptibility around Zn.