${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ NMR study of spin dynamics in ${\mathrm{Sr}}_2$${\mathrm{CuO}}_2$${\mathrm{Cl}}_2$

Measurements of the ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ nuclear-spin–lattice relaxation rate (NSLR) are reported for ${\mathrm{Sr}}_2$${\mathrm{CuO}}_2$${\mathrm{Cl}}_2$ around the antiferromagnetic transition temperature ${\mathit{T}}_{\mathit{N}}$=260±0.5 K. The temperature dependence of the ${\mathrm{Cu}}^{2+}$ spin correlation length ξ(T) is obtained indirectly by using the conventional description of NSLR and scaling arguments and compared with the ξ(T) obtained in ${\mathrm{La}}_2$${\mathrm{CuO}}_4$ by neutron scattering. In both systems ξ(T) follows the two-dimensional Heisenberg behavior renormalized by quantum fluctuations except close to ${\mathit{T}}_{\mathit{N}}$ where a crossover to a power-law T dependence is observed in ${\mathrm{Sr}}_2$${\mathrm{CuO}}_2$${\mathrm{Cl}}_2$.