MAGNETIC PROPERTIES OF COBALT FERRITE/COBALT IRON NANOCOMPOSITES PRODUCED BY RAPID HYDROGEN REDUCTION

Abstract

This work investigates the magnetic properties of cobalt ferrite (CoFe2O4) and cobalt iron (CoFe) nanocomposites, synthesized by a rapid hydrogen reduction method. Pre-milled CoFe2O4 samples were subjected to thermal treatment in a tubular furnace under a hydrogen atmosphere (99.99% purity) at 350°C, with times ranging from 10 to 30 minutes. Magnetic measurements, performed by vibrating sample magnetometry (VSM), revealed the formation of an exchange-spring interaction between the magnetically hard (CoFe2O4) and soft (CoFe) phases, evidenced by smooth and continuous hysteresis loops. A notable increase in saturation magnetization (Ms) was observed, from 64(3) emu/g to 176(20) emu/g in 30 minutes, attributed to the increasing formation of CoFe, which has a higher Ms. In contrast, remanent magnetization (Mr) and coercivity (Hc) significantly decreased with reduction time, from 36(1.8) emu/g to 20(1) emu/g and from 3.4(2) kOe to 0.3(0.1) kOe, respectively. The maximum energy product ([BH]max also decreased from 9.6(5) kJ/m³ to 1.0(0.5) kJ/m³. These trends confirm the magnetically soft nature of the formed CoFe and the material's transition from a semi-hard to a softer character. The results demonstrate the effectiveness of the rapid reduction method in modulating the magnetic properties of these nanocomposites, offering a promising approach for materials with tunable properties for various technological applications.