Fig. 4. SAR values in the low frequency range of aqueous suspension of (a) ε-Fe₂O₃ NPs and (b) γ-Fe₂O₃ NPs in as a function of health parameter Hf. SAR values in the high frequency range of aqueous suspensions of (c) ε-Fe₂O₃ NPs and (d) γ-Fe₂O₃ NPs. In the insets, details of the SAR in the health safety range of Hf. Shaded areas mark the health safety region in a–d. SAR vs. Hf at different NP mobility conditions of (e) ε-Fe₂O₃ NPs and (f) γ-Fe₂O₃ NPs.