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Tuning the magnetization dynamics of silica-coated Fe<inf>3</inf>O <inf>4</inf> core-shell nanoparticles by shell thickness control
Date Issued
21-04-2008
Author(s)
Mohan Kant, K.
Indian Institute of Technology, Madras
Indian Institute of Technology, Madras
Abstract
Core-shell silica (Si O2) -coated Fe3 O4 nanoparticles of shell thickness between 2 and 52 nm have been synthesized and characterized. The saturation magnetization scales with Si O2 wt % and these samples exhibit negligible hysteresis at room temperature, as compared to the bulk Fe3 O4. The peak in the temperature-dependent ac susceptibility Tm shifts toward higher temperature with increasing frequency. Data of pristine to 40 wt % Si O2 -coated samples fit to critical slowing-down behavior model yielding relaxation time of ∼ 10-10 s. For particles of higher shell thickness, smaller relaxation time of ∼ 10-13 s is obtained. Temperature-dependent electron spin resonance measurements suggest overall weakening of magnetic interactions in Fe3 O4 nanoparticles of thicker Si O2 shell. Variation of shell thickness in these core-shell nanoparticles could lead to diverse ground states ranging from interacting to noninteracting systems. © 2008 American Institute of Physics.
Volume
103