Theory of nuclear spin–lattice relaxation inLa2CuO4at high temperatures

Abstract

The nuclear-spin–lattice relaxation in ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$ is reexamined in connection with the recent measurements of the NQR relaxation rate for temperatures up to 900 K [T. Imai, C. P. Slichter, K. Yoshimura, and K. Kosuge, Phys. Rev. Lett. 70, 1002 (1993)]. We use an approach based on the exact diagonalization for the Heisenberg model to calculate the short-wavelength contribution to the relaxation rate in the high-temperature region, T≳J/2. It is shown that the spin diffusion accounts for approximately 10% of the total relaxation rate at 900 K and would beome dominant for T>J. The calculated 1/${\mathit{T}}_1$ is in good agreement with the experiment both in terms of the absolute value and temperature dependence.