Fig. 6. (a) Experimental (black) and simulated (red) two-pulse echo detected field-swept ESR spectrum of Cu_0.1-PCN-223 recorded at T = 80 K. The tensor values g_‖ = 2.2 and g_⊥ = 2.06 labeled by arrows indicate the magnetic field spectral positions at which spin dynamics was undertaken. (b) Temperature dependence of the electron spin–lattice relaxation rate, 1/T₁, of Cu_0.1-PCN-223 (black), 0.2C₆₀@Cu_0.1-PCN-223 (blue) and 1.0C₆₀@Cu_0.1-PCN-223 (red) measured at g_‖ spectral position. Full lines denote best-fits of the experimental data according to the eqn (2) with the parameters given in Table 1. In the inset to the figure, magnetization recovery curves are given in the inversion recovery experiment detected at 5 K. (c) Temperature dependence of the electron-spin phase-memory relaxation time, T_m, in various MOFs at g_‖ spectral position.