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. 2018 Jul 24;8:11166. doi: 10.1038/s41598-018-29501-8

Figure 1.

Figure 1

The reduced magnetisation as a function of temperature for a field-cooled (FC, solid lines) and zero-field-cooled (ZFC, dashed lines) random assembly of particles, calculated three different ways. Panel (a) shows the reduced magnetisation calculated using Eqs (1 and 2). Fe2O3 particles all with 5 nm radius are considered (Ms = 281 kA/m and K = 16 kJ/m3) with a weak applied field H = 10 Oe (796 A/m). These parameters are chosen to match ref.13. In panel (b), the magnetisation curves are re-drawn using a log-normal distribution of particle sizes with dispersion σ = 0.02 using Eqs (5 and 6) and the sharp peak is smoothed out. In panel (c) our weighted-probability expressions, to be developed later in the text in Eqs (10 and 11), are drawn for particles of a single size and show a similar shape to the plots in panel (b) where a size distribution is assumed. The measurement time is taken to be ln (τm/τ0) = 25. The vertical line in panels (b) and (c) indicates the mode blocking temperature, to the left of the ZFC peak.