Fig. 4: Nuclear spin-lattice relaxation of YCu3(OH)6.5Br2.5.
From: The observation of quantum fluctuations in a kagome Heisenberg antiferromagnet
a A representative T = 2.8 K spin-lattice relaxation of Br1 measured by an inversion recovery method, fitted to the stretched-exponential function with fixing β = 1 (red) and tuning β (blue). The pulse sequence for T1 measurements is depicted in the inset. b The same fits to the relaxation data measured at other selected temperatures. The inset shows the fitted stretching exponent β. c Temperature dependence of 81Br1 nuclear spin-lattice relaxation rate 1/T1 measured on the sample S1 at a field μ0H∥ = 10.75 T, as well as 81Br1 and 79Br1 1/T1 measured on S2 at μ0H∥ = 10.75 and 11.59 T, respectively. The colored lines present the power-law fits to the experimental data below ~ 10 K ~ 0.2〈J1〉, the dashed black and blue lines are the 1/T1 and energy (per site), respectively, calculated by using the random kagome Heisenberg antiferromagnet model of YCu3(OH)6.5Br2.5. d The Curie (~T−1, black lines) and critical (~(T − Tc)\({}^{-\alpha ^{\prime} -1}\), the critical temperature Tc = − 0.1 ± 0.4 K, green lines) fits to 1/(T1T) at 1.7 ≤ T ≤ 300 K. The blue line is the low-T power-law dependence as shown in c. The inset shows the T1T vs T plot, where the dashed violet line displays the antiferromagnetic Curie-Weiss behavior (T1T ~ T + 〈J1〉, with coupling 〈J1〉 ~ 50 K). The T1 data presented in c and d are obtained from the single-exponential fits (i.e., β = 1, see a and b), and the stretched-exponential fits are made only for comparison in a and b. Error bars on the experimental data points show a standard error from fit, and the error bars in a and b are small.
