Nuclear Relaxation of Hydrogen-Doped Antiferromagnetic YBa₂Cu₃O₆+{x}H_y

Abstract

Cu(1) NQR, Cu(2) zero field NMR, and proton NMR have been measured in the antiferromagnetic (AF) phase of a powdered sample of hydrogen-doped YBa₂Cu₃O_6.1H_0.14 from 4.2 to 300, K. The line width of ¹H NMR increases abruptly below 20, K. The enhancements of T₂^-1 and T₁^-1 of ⁶³Cu(1) NQR occur around 20 and 40, K, respectively. The relaxation mechanism of T₁ of NQR changes at T_rm=80, K and the time dependence of its nuclear magnetization recovery shows a nonexponential type for Trm and an exponential one for T>T_rm. The predominant source for T₁ below T_rm is found to be the fluctuating magnetic fields due to the staggered Cu²⁺ moments induced by the hole doping effect. Above T_rm, T₁^-1 of NQR increases gradually with temperature but it is almost temperature independent above 150, K, what can not be explained by the effect of the ordered AF Cu²⁺ moments in the Cu(2)O₂ plane and also by the Raman process of the lattice vibrations.