Magnetic properties of γ-Fe₂O₃ nanoparticles prepared by laser ablation

Abstract

A new method of preparing nanoparticles by pulsed-laser ablation of a tiny wire was reported, and pure maghemite (γ-Fe₂O₃) nanoparticles were synthesized by this method in a mixed gas flux of N₂ and O₂ at atmospheric pressure. The obtained γ-Fe₂O₃ nanopartiles were in the runge of 5 to 80 nm in diameter and largely spherical in shape. Structural characteristics and morphologies of the nanoparticles were characterized by XRD and TEM, respectively. Moreover, magnetic properties of the obtained γ-Fe₂O₃ nanopartiles in the temperature range of 300 to 773 K were investigated. The experimental results demonstrate that the squareness value of the hysteresis loop decreases with increasing temperature. Both the coercivity and the saturation magnetization of the γ-Fe₂O₃ nanoparticles show a constantly decreasing trend with increasing temperature up to the occurrence of the transformation from γ-Fe₂O₃ to α-Fe₂O₃. Especially, at the temperature of 773 K, the γ-Fe₂O₃ begins to transform to the α-Fe₂O₃ phase and the hysteresis loop becomes unclosed.

Keywords

maghemite / nanoparticles / laser ablation / magnetic properties

References

[1] Ziolo R F, Giannelis E P, Weinstein B A, . Matrix Mediated Synthesis of γ-Fe₂O₃: A New Optically Transparent Magnetic Material[J]. Science, 1992, 257: 219-222.

[2] Awschalom D D, Di Vincenzo D P. Complex Dynamics of Mesoscopic Magnets[J]. Physics Today, 1995, 4: 43-48.

[3] Miser Donald E, Shin Eun-Jae, Mohammad R Hajaligol, Firooz Rasouli. HRTEM Characterization of Phase Changes and the Occurrence of Maghemite during Catalysis by an Iron Oxide[J]. Appl. Catal. A: General, 2004, 258: 7-16.

[4] S Banerjee S, Roy J, Chen W, Chakravorty D, . Magnetic Properties of Oxide-coated Iron Nanoparticles Synthesized by Electrodeposition[J]. J. Magn. Magn. Mater., 2000, 219: 45-52.

[5] Woo Kyoungja, Jin Lee Ho. Synthesis and Magnetism of Hematite and Maghemite Nanoparticles[J]. J. Magn. Magn. Mater., 2004, 272–276: E1155-E1156.

[6] Tronc E, Ezzir A, Cherkaoui Chanéac C R, Noguès M, Kachkachi H, . Surface-related Properties of γ-Fe₂O₃ Nanoparticles[J]. J. Magn. Magn. Mater., 2000, 221: 63-79.

[7] Vollath D, Szabó D V, Taylor R D, . Synthesis and Properties of Nanocrystalline Superparamagnetic γ-Fe₂O₃[J]. Nanostr. Mater., 1995, 6: 941-944.

[8] Liao X, Zhu J, Zhong W, Chen H Y. Synthesis of Amorphous Fe₂O₃ Nanoparticles by Microwave Irradiation[J]. Mater. Lett., 2001, 50: 341-346.

[9] Sasaki T, Terauchi S, Koshizaki N, Umehara H. Preparation of Nanoparticles by Excimer Laser Ablation of Calcium Iron Complex Oxide[J]. Ceram. Proc., 1997, 43(11A): 2636-2640.

[10] Zeng X, Wang Z, Liu Y, . γ-Fe₂O₃ Nanoparticles Prepared by Laser Ablation of a Tiny Wire[J]. Appl. Phys. A: Mater. Sci. Process, 2005, 80(3): 581-584.

[11] Majetich S A, Scott J H, Kirkpatrick E M., . Magnetic Nanoparticles and Magnetocrystalline Anisotropy[J]. Nanostr. Mater., 1997, 9: 291-300.

[12] Jônsson B J, Turkki T, Ström V, El-Shall M S, Rao K V. Oxidation States and Magnetism of Fe Nanoparticles Prepared by a Laser Evaporation Technique[J]. J. Appl. Phys., 1996, 79(8): 5063-5065.