Surface-induced superparamagnetic relaxation in nanoscale ferrihydrite particles

Journal Article · Thu Aug 01 04:00:00 EDT 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.54.3403· OSTI ID:288840

Zhao, J; Huggins, F E; Feng, Z; Huffman, G P ^[1]

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1. The Consortium for Fossil Fuel Liquefaction Science, 341 Bowman Hall, University of Kentucky, Lexington, Kentucky 40506 (United States)

The effect of surface on superparamagnetic relaxation for nanoscale ferrihydrite particles ({ital d}{approximately}5 nm) has been investigated using M{umlt o}ssbauer spectroscopy. With increasing surface chemisorption of SiO{sub 4}{sup 4{minus}}, the superparamagnetic transition temperature ({ital T}{sub {ital B}}) falls from 100 to 40 K and the transition sharpens. This indicates that the SiO{sub 4}{sup 4{minus}} species eliminate the surface unpaired spins and create a nonmagnetic medium, thereby significantly reducing the magnetic coupling between the particles. For ferrihydrite particles impregnated on a silica support, the particle interaction becomes negligible and the superparamagnetic transition occurs at a still lower temperature of {approximately}12 K; the spectra exhibit characteristic size-dependent features. {copyright} {ital 1996 The American Physical Society.}

• DOE Contract Number: FC22-93PC93053
• OSTI ID: 288840
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 5 Vol. 54; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHEMISORPTION
FERRITES
FLUCTUATIONS
MAGNETIC MOMENTS
MAGNETIZATION
MOESSBAUER EFFECT
NANOSTRUCTURES
RELAXATION TIME
SUPERPARAMAGNETISM
SURFACE PROPERTIES
TRANSITION TEMPERATURE