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Appl. Sci. 2017, 7(12), 1269; https://doi.org/10.3390/app7121269

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

1
Department of Physics, United Arab Emirates University, Al-Ain 15551, UAE
2
Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Straße-40, 01187 Dresden, Germany
*
Author to whom correspondence should be addressed.
Received: 31 October 2017 / Revised: 15 November 2017 / Accepted: 21 November 2017 / Published: 5 December 2017
(This article belongs to the Special Issue Biological Applications of Magnetic Nanoparticles)
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Abstract

Understanding saturation magnetization and its behavior with particle size and temperature are essential for medical applications such magnetic hyperthermia. We report the effect of shell thickness and field cooling on the saturation magnetization and its behavior with temperature in Fe3O4/γ-Fe2O3 core/shell nanoparticles of fixed core diameter (8 nm) and several shell thicknesses. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM, high-resolution transmission electron microscopy (HRTEM)) were used to investigate the phase and the morphology of the samples. Selected area electron diffraction (SAED) confirmed the core/shell structure and phases. Using a SQUID (San Diego, CA, USA), magnetic measurements were conducted in the temperature range of 2 to 300 K both under zero field-cooling (ZFC) and field-cooling (FC) protocols at several field-cooling values. In the ZFC state, considerable enhancement of saturation magnetization was obtained with the increase of shell thickness. After field cooling, we observed a drastic enhancement of the saturation magnetization in one sample up to 120 emu/g (50% larger than the bulk value). In both the FC and ZFC states, considerable deviations from the original Bloch’s law were observed. These results are discussed and attributed to the existence of interface spin-glass clusters which are modified by the changes in the shell thickness and the field-cooling. View Full-Text
Keywords: nanoparticles; magnetization; shell thickness; Bloch’s law nanoparticles; magnetization; shell thickness; Bloch’s law
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Obaidat, I.M.; Nayek, C.; Manna, K. Investigating the Role of Shell Thickness and Field Cooling on Saturation Magnetization and Its Temperature Dependence in Fe3O4/γ-Fe2O3 Core/Shell Nanoparticles. Appl. Sci. 2017, 7, 1269.

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