Investigating Size- and Temperature-Dependent Coercivity and Saturation Magnetization in PEG Coated Fe3O4 Nanoparticles

Abstract

Polyethylene glycol (PEG) coated magnetic Fe 3 O 4 nanoparticles with diameters of 12 nm, 15 nm, and 16 nm were synthesized by the usual co-precipitation method. The structure and morphology of the samples were characterized using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The ac magnetic susceptibility measurements were carried out using a vibrating sample magnetometer (VSM). The dc magnetic measurements were carried out using a commercial Quantum Design superconducting quantum interference device (SQUID). The XRD patterns indicated the sole existence of the inverse cubic spinel phase of Fe 3 O 4 in all the samples. The histograms extracted from the TEM images show narrow size distributions with average sizes that are very similar to those obtained from the XRD images using the Scherrer's formula. The temperature dependence of both coercivity and saturation magnetization, which were determined from the magnetic hysteresis loops, were found to have considerable deviations from the Bloch's and Kneller's laws. The size-dependent coercivity and saturation magnetization were found to be non-monotonic at nearly all temperatures. These results are discussed and attributed mainly to the finite size effects in addition to the existence of inter-particle interactions and of spin-glass structures that resulted from frozen canted surface spins at low temperatures.

Structural, Optical, and Isothermic Studies of CuFe2O4 and Zn‐Doped CuFe2O4 Nanoferrite as a Magnetic Catalyst for Photocatalytic Degradation of Direct Red 264 Under Visible Light Irradiation

“…The observed value of saturation magnetization ( M s ) was 24 emu/g. The magnetic susceptibility of CuFe 2 O 4 was found to be smaller than that of the bulk one and decreases with the decrease in particle size due to the disorder canting spins on the surfaces .…”

Synthesis of Graphene Oxide-Fe3O4 Based Nanocomposites Using the Mechanochemical Method and in Vitro Magnetic Hyperthermia

“…The XRD pattern of GO-Fe with a 20:80 composition showed peaks corresponding to Fe and Fe 3 O 4 phases. The peaks corresponding to Fe 3 O 4 phase had less intensity compared to the Fe phase, which indicates that the presence of a lesser amount of graphene oxide results in suppressed oxidation of Fe, whereas in the case of a 50:50 composition, the Fe powder was completely oxidized into Fe 3 O 4 phase [26,27]. In the case of the 80:20 composition, the nanocomposite had XRD peaks corresponding to both Fe 3 O 4 and Fe 2 O 3 , which can be attributed to the role of graphene oxide.…”

Investigating the Role of Shell Thickness and Field Cooling on Saturation Magnetization and Its Temperature Dependence in Fe3O4/γ-Fe2O3 Core/Shell Nanoparticles

“…Most models that are used to understand the heating process are based on Rosensweig's theory [22] where, as an approximation, the saturation magnetization is considered to be constant with temperature. However, it is well-established that the saturation magnetization of nanoparticles changes significantly with temperature [23][24][25][26][27][28].…”