Figure 6.

Principal features of magnetic material: (a) Hysteresis loop of ferromagnetic and ferrimagnetic materials. Critical magnetic parameters: Saturation magnetization (M_s), Coercive field (H_c), and Remnant Magnetization (M_r) are shown. (b) Magnetization behavior of ferromagnetic and superparamagnetic NPs under an external magnetic field. Domains of a ferromagnetic NP align with the applied fields. The magnetic moment of single domain superparamagnetic NPs aligns with the applied field. In the absence of an external field, ferromagnetic NPs will maintain a net magnetization, whereas superparamagnetic NPs will exhibit no net magnetization due to rapid reversal of the magnetic moment. The relationship between NP size, the magnetic domain structures, and coercive field is shown. Ds and Dc are the ‘superparamagnetism’ and ‘critical’ size threshold. Modified from Reference [77].