Synthesis, characterization and magnetic properties of hollow Co 2 FeAl nanoparticles: the effects of heating rate

• Published in: New journal of chemistry 2016, Vol.40 (6), p.5061-5070
• Main Authors: Almasi-Kashi, Mohammad, Ramazani, Abdolali, Alikhanzadeh-Arani, Sima, Pezeshki-Nejad, Zahra, Hassan Montazer, Amir
• Format: Article
• Language: English
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/C6NJ00646A

Magnetic hollow nanoparticles (HNPs) are of particular interest owing to their broad applications including targeted drug delivery and magnetic resonance imaging. Here, hollow Co 2 FeAl full-Heusler NPs were successfully synthesized using the polyethylene glycol polymer as a capping agent, followed by thermal annealing at 700 °C with heating rates ranging between 5 and 15 °C min −1 . Increasing the heating rate up to 15 °C min −1 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 g −1 and coercivity of 730 Oe were obtained using heating rates of 5 and 10 °C min −1 , 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, the average coercivity obtained from hysteresis curve was approached to FORC coercivity.