Size dependent magnetic properties and cation inversion in chemically synthesized MnFe₂O₄ nanoparticles
Originally published in Journal of Applied Physics 101, 09M509 (2007). DOI:10.1063/1.2710218 (http://dx.doi.org/10.1063/1.2710218).
MnFe₂O₄ nanoparticles with diameters ranging from about 4 to 50 nm were synthesized using a modified coprecipitation method. X-ray diffractograms revealed a pure phase spinel ferrite structure for all samples. Transmission electron microscopy showed that the particles consist of a mixture of both spherical (smaller) and cubic (larger) particles dictated by the reaction kinetics. The Néel temperatures (TN) of MnFe₂O₄ for various particle sizes were determined by using high temperature magnetometry. The ∽4 nm MnFe₂O₄ particles showed a TN of about 320°C whereas the ∽50 nm particles had a TN of about 400°C. The high Neel temperature, compared with the bulk MnFe₂O₄ TN of 300°C, is due to a change in cation distribution between the tetrahedral and octahedral sites of the spinel lattice. Results of extended x-ray absorption fine structure measurements indicate a systematic change in the cation distribution dependent on processing conditions.
C. N. Chinnasamy, Aria Yang, S. D. Yoon, Kailin Hsu, M. D. Shultz, E. E. Carpenter, S. Mukerjee, C. Vittoria, and V. G. Harris. "Size dependent magnetic properties and cation inversion in chemically synthesized MnFe₂O₄ nanoparticles" Electrical and Computer Engineering Faculty Publications (2007).
Available at: http://works.bepress.com/vharris/25