1. Surface Spin Disorder in Fe3 O4 Nanoparticles Probed by Electron Magnetic Resonance Spectroscopy and Magnetometry.
- Author
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Pal, S., Dutta, P., Shah, N., Huffman, G. P., and Seehra, M. S.
- Subjects
IRON ,MAGNETIC resonance ,SPECTRUM analysis ,MAGNETISM ,ELECTRONS - Abstract
SQUID magnetometry and electron magnetic resonance (EMR) spectroscopy at 9.28 GHz were employed to probe magnetism and surface spin disorder in Fe
3 O4 nanoparticles. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis showed magnetite particles with size ≃8 nm. Magnetization (M) versus temperature studies yielded blocking temperature TB ≃ 170 K in H = 50 Oe. For T > TB , M scales approximately as H/T with μP ≃ 5400 μB as the magnetic moment/particle. At 5 K, the magnitudes of hysteresis loop parameters viz. coercivity Hc ≃ 37 Oe and saturation magnetization M8 = 62 emu/g are considerably smaller than the reported values for larger 150 nm Fe3 O4 particles. In EMR studies, a single symmetric line at g ≃ 2.11 with linewidth ΔH = 850 Oe is observed at 300 K with the g-value and ΔH increasing with decreasing T. These results are interpreted in terms of a disordered surface spin layer of 0.5 nm thickness. [ABSTRACT FROM AUTHOR]- Published
- 2007
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