SQUID magnetometry for solid nitroxide tetraradical 1 with numerical fits to the tetraradical model, using J2/k = 0 (Figure 10, equations 1 and 2). The variable parameters (parameter dependence and R2) are as follows: at 1.8 K, J1/k = −0.6 K, Msat = 0.94 μB (0.75, 1.000); at 3 K, J1/k = −0.5 K, Msat = 0.95 μB (0.94, 1.000); at 5000 Oe in the warming mode, J1/k = −0.6 K, w = 0.96 (0.23, 0.993).