Influence of the size of particles on the magnetic heating of a mixed ferrite

Starting from a mixed ferrite of commercial origin, we obtained six samples in the form of powder by crushing and sieving. From each powder sample, the same mass of powder was taken and added to 1 ml of water and the time dependence of the temperature increase (ΔT(t)) of the aqueous suspensions has been measured during the heating in alternating magnetic field with the amplitude of 8.4 kA/m and frequency of 100 kHz. The results showed that ΔT(t) depends on the size of particles and the sample with particle diameters ranging between 200 µm and 315 µm exhibited the largest heating rate, ΔT/Δt. The results are explained in terms of combined dependence of the energy absorption from the electromagnetic field on the particle size and on the particle packing fraction.