Preparation and Properties of FeCo Nanoparticles

Abstract

Fe-Co nanoparticles were prepared from the double Fe-and Co-oxalate. The formation of FeCo metallic phase (solid solution) begun at 250 °C as determined from the Xray diffraction spectra recorded during heating of the oxalate sample in reducing atmosphere. The reduction finished at 500 °C by formation of α-FeCo phase with the mean particle size of about 17 nm. The final product was investigated using Mössbauer spectroscopy, transmission electron microscopy (TEM), and magnetic measurements. Analysis of Mössbauer spectra shows the ferromagnetic α-FeCo phase represented by two six-line patterns corresponding to interiors and surfaces of the nanoparticles. The hyperfine inductions of these components are 34.06 for the first one and 35.03 T with hypefine field distribution 34.22 T for the second one. In addition to a weak paramagnetic component represented by the doublet with isomer shift 0.14 mm/s and quadrupole splitting 0.49 mm/s was found. The doublet was ascribed to fine particles in superparamagnetic state. The TEM has shown conglomerates of particles with composition about 50 at. % Fe and 50 at. % Co.

Size Controlled Synthesis of FeCo Alloy Nanoparticles and Study of the Particle Size and Distribution Effects on Magnetic Properties

“…Magnetic nanoparticles are a topic of growing interest because of their versatile applications such as ultrahigh density data storage, drug delivery, magnetic separation and MRI contrast enhancement [1][2][3][4][5][6][7][8][9][10][11][12][13]. Among those, magnetic hyperthermia is a novel therapeutic method in which the magnetic nanoparticles are subjected to an alternating magnetic field to generate a specific amount of heat.…”

“…The generated heat will then raise the temperature of the tumor to about 42 ∘ C at which certain mechanisms of cell damage are activated [14]. The heat producing mechanisms under A.C. magnetic fields are (1) hysteresis, (2) the Neel or Brownian relaxation, (3) viscous losses [15].…”

“…FeCo alloy has the highest saturation magnetization among all binary magnetic alloys [1]. Several methods have been used to synthesize FeCo alloy nanoparticles which include arc discharge [2], polyol [3][4][5][6][7], hydrothermal [8], reaction under autogenic pressure at elevated temperature (RAPET) [9], thermal decomposition [10], wet chemical [11,12], and coprecipitation [13,17,18]. The morphology and size distribution of as-synthesized nanoparticles are not well controlled in most of these processes.…”