Exploring the effect of Co concentration on magnetic hyperthermia properties of CoxFe3−xO4 nanoparticles

Although enhanced ferrite nanoparticles (NPs) have been envisioned for use in future biomedical applications, less attempt has been made to tailoring and optimizing their detailed magnetic properties and specific loss power (SLP) values. Herein, CoxFe3−xO4 (0 ≤ × ≤ 1) NPs are synthesized using a co-precipitation method at 80 °C in the presence of air atmosphere. The effect of varying Co concentration on crystalline, morphological, magnetic and hyperthermia properties is also investigated in detail. Hysteresis loop measurements showed an increase in coercivity (Hc) from 7.75 to 340.50 Oe, and a decrease in saturation magnetization (Ms) from 59.10 to 32.70 emu g−1 with increasing x = 0 (pure magnetite) to x = 1 (pure Co ferrite), respectively. In addition to confirming the hysteresis loop results, first-order reversal curve (FORC) analysis estimated a 52% decrease in superparamagnetic (SP) fraction. Hyperthermia measurements carried out under an alternating magnetic field with intensity of 400 Oe and a frequency of 400 kHz showed an increase in SLP from x = 0 to x = 0.4, and a decrease in SLP for 0.4 < × ≤ 1. SLP was maximized at 395 W g−1 for the intermediate concentration of x = 0.4. The optimized heat generation of Co0.4Fe2.6O4 NPs comprising approximately 50%-50% SP-ferromagnetic fractions may result from the simultaneous contribution of the three following mechanisms: hysteresis loop loss, Brownian and Neel relaxation together with relatively high Hc and moderate Ms.