Variations of magnetization with reduced crystal field Δ/J_aa (a) for T/J_aa = 1.0, 2.0, 2.5, 3.0, R₂ = 1 and l_a = 5, (b) for R₂ = 1.0, 2.0, 3.0, 5.0, T/J_aa = 1 and l_a = 5, and (c) for l_a = 5, 7, 9, 11, T/J_aa = 1 and R₂ = 1 with h/J_aa = 0.4.