Polymer-mediated synthesis of γ-Fe 2O 3 nano-particles

• Published in: Polyhedron Vol. 20; no. 11; pp. 1489 - 1494
• Main Authors: Radhakrishnan, S, Saujanya, C, Sonar, P, Gopalkrishnan, I.K, Yakhmi, J.V
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2001
• Subjects: Iron(III) oxide; Magnetic characterization; Nano-particles; Synthesis; Magnetic characterization; Synthesis; Nano-particles; Iron(III) oxide
• ISSN: 0277-5387
• DOI: 10.1016/S0277-5387(01)00640-4

Nano-particles of γ-Fe 2O 3 were synthesized by reacting polyethylene oxide–FeCl 3 complex with NH 4OH. These were characterized by X-ray diffraction (XRD), scanning electron miscroscopy (SEM), selected area electron diffraction (SAED) and transmision electron microscopy (TEM). The average particle size was found to be 10 nm, as determined from the line broadening of the main XRD peak. The crystalline phase was a spinel-type tetragonal structure, which was confirmed from the electron diffraction pattern. The zero field cooled magnetization of samples with varying γ-Fe 2O 3 content as a function of temperature was measured using a vibrating sample magnetometer. The magnetization curves show a peak at low temperature (15 K) corresponding to the blocking temperature T B. The value of T B was found to decrease with decreasing particle size. The magnetization measurements with respect to field at 5 and 170 K confirmed the transition from superparamagnetic to spin-glass state at T B, as evidenced from the remanence and hysteresis. These results can be explained on the basis of Néel's theory of superparamagnetism as applied to nano-particles.