Magnetism and spin dynamics of nanoscale FeOOH particles

Journal Article · Sun May 15 04:00:00 EDT 1994 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.355545· OSTI ID:7283910

Ibrahim, M M; Edwards, G; Seehra, M S ^[1]; Ganguly, B; Huffman, G P ^[2]

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1. Physics Department, West Virginia University, P. O. Box 6315, Morgantown, West Virginia 26506-6315 (United States)
2. Consortium for Fossil Fuel Liquefaction Science, 233 Mining and Mineral Resources Building, University of Kentucky, Lexington, Kentucky 40506 (United States)

The nature of magnetism and electron paramagnetic resonance (EPR) spin dynamics in 30 A particles of FeOOH have been investigated in the range 5--350 K. X-ray diffraction shows that the particles are neither [alpha]-Fe[sub 2]O[sub 3] nor [alpha]-FeOOH based and they convert to Fe[sub 3]O[sub 4] ([alpha]-Fe[sub 2]O[sub 3]) on heating to 800 K in vacuum (air). Magnetization [ital M] vs [ital T] data show a blocking temperature [ital T][sub [ital B]] in the range 40 K[lt][ital T][sub [ital B]][lt]100 K so that for [ital T][ge]100 K, scaling of [ital M] with [ital H]/[ital T] for [ital H] up to 50 kOe verifies superparamagnetism. In EPR, both the linewidth [Delta][ital H] and the [ital g] value decreases upon increasing [ital T] so that near 300 K, [ital g][congruent]2.05 (characteristic of Fe[sup 3+]). A model of motional narrowing is used to explain the [Delta][ital H] vs [ital T] behavior. The dramatic changes in [ital M], [Delta][ital H], [ital g] value, and the recoilless fraction of Moessbauer spectroscopy observed near 50 K are all related to the thermal motion of the superparamagnetic nanoscale particles.

• OSTI ID: 7283910
• Journal Information: Journal of Applied Physics; (United States), Journal Name: Journal of Applied Physics; (United States) Vol. 75:10; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
CHALCOGENIDES
COHERENT SCATTERING
DIFFRACTION
ELECTRON SPIN RESONANCE
HYDROGEN COMPOUNDS
HYDROXIDES
IRON COMPOUNDS
IRON OXIDES
MAGNETIC PROPERTIES
MAGNETIC RESONANCE
MOESSBAUER EFFECT
OXIDES
OXYGEN COMPOUNDS
PARTICLES
PARTICULATES
PHASE STUDIES
PHYSICAL PROPERTIES
RESONANCE
SCATTERING
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION