Fig. 1.
Logarithmic 2D plot of the effective relaxation time combining Néel (abscissa, Eq. 4) and Brownian relaxation (ordinate, Eq. 5) according to Eq. 6. Furthermore, the corresponding core and hydrodynamic diameter are displayed for magnetite MNP with an effective anisotropy K ~ 104 J/m3. The straight lines have been added to show the influence of a fixed shell thickness of 5 nm (white line), 10 nm (red line) or a fixed hydrodynamic diameter of 150 nm (orange line) and 160 nm (black line) on the relaxation time with increasing core diameter.