Fig. 4. (a) Saturation magnetization of Ni_xZn_1−xFe₂O₄ nanoparticles at 300 K and 5 K, effective anisotropy, and inversion (Ni²⁺ at B-site) with respect to Ni²⁺ concentration. (b) The interrelation of magnetic size (D_max, nm) and non-magnetic layer (t_cant, nm).