Synthesis, characterization and magnetic Q۱ Q۲ properties of hollow Co۲FeAl nanoparticles: the effects of heating rate

Abstract

Magnetic hollow nanoparticles (HNPs) are of particular interest owing to their broad applications including targeted drug delivery and magnetic resonance imaging. Here, hollow Co2FeAl full-Heusler NPs were successfully synthesized using the polyethylene glycol polymer as a capping agent, followed by thermal annealing at 700 1C with heating rates ranging between 5 and 15 1C min1. Increasing the heating rate up to 15 1C min1 decreased the mean particle size, as characterized by scanning and transmission electron microscopy (TEM). High resolution TEM images revealed the highly crystalline nature of the HNPs with different grain size. A maximum saturation magnetization of 95 emu g1 and coercivity of 730 Oe were obtained using heating rates of 5 and 10 1C min1, respectively. Alternatively, first-order reversal curve (FORC) measurements at room temperature revealed the formation of a mixture of single-domain and superparamagnetic (SP) grains due to the presence of a wide range of particle sizes. With the increase in the heating rate, the SP contribution increased, which resulted in a decrease in the inter-particle magnetostatic interactions, thereby approaching the average coercivity obtained from the hysteresis curve to FORC coercivity.