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Title: Neutron scattering and magnetic studies of ferrihydrite nanoparticles

Abstract

Magnetic properties of two-line ferrihydrite (FeOOD{center_dot}nD{sub 2}O) nanoparticles with an average size {approx_equal}4 nm are investigated using neutron scattering and magnetometry. Comparison of the neutron scattering and x-ray diffraction patterns identifies the (002) peak at Q=1.3 Aa{sup -1} as predominantly magnetic. The intensity of this peak, measured from 10 to 450 K, decreases almost linearly with temperature until 350 K, becoming temperature independent above 350 K. From this, T{sub N}{approx_equal}350 K is identified to be the ordering temperature of the core spins of the nanoparticles. The width of the line is temperature independent, yielding a magnetic coherence length(approx =)particle size. The temperature variations (5-300 K) of the initial susceptibility {chi} for the field-cooled (FC) and zero-field-cooled (ZFC) cases yield a peak at T{sub p}(m){approx_equal}65 K, below which {chi}(FC)>{chi}(ZFC). For T>T{sub p}(m), the variation of {chi}{sup -1} vs T is analyzed in terms of the model of El-Hilo et al., involving particle-size distribution and interparticle interactions, and substantial interparticle interactions are inferred. Following the observations in ferritin, the field dependence of the magnetization M for T>T{sub p}(m) is analyzed in terms of the modified Langevin variation: M=M{sub o}L({mu}{sub p}H/kT)+{chi}{sub a}H, where {mu}{sub p} is the magnetic moment/particle. The fit at 100more » K yields {mu}{sub p}{approx_equal}250 {mu}{sub B}, consistent with the theoretical estimates based on uncompensated surface spins of Fe{sup 3+}. (c) 2000 The American Physical Society.« less

Authors:
 [1];  [1];  [1];  [2]
  1. Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)
  2. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8562 (United States)
Publication Date:
OSTI Identifier:
20215333
Resource Type:
Journal Article
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 61; Journal Issue: 5; Other Information: PBD: 1 Feb 2000; Journal ID: ISSN 1098-0121
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; IRON HYDRIDES; NEUTRON DIFFRACTION; MAGNETIC PROPERTIES; X-RAY DIFFRACTION; MAGNETIZATION; TEMPERATURE RANGE 0000-0013 K; TEMPERATURE RANGE 0013-0065 K; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0400-1000 K; TEMPERATURE RANGE 0273-0400 K; SPIN; NEEL TEMPERATURE; MAGNETIC SUSCEPTIBILITY; PARTICLE SIZE; MAGNETIC MOMENTS; FERRIMAGNETIC MATERIALS; EXPERIMENTAL DATA; THEORETICAL DATA

Citation Formats

Seehra, M S, Babu, V S, Manivannan, A, and Lynn, J W. Neutron scattering and magnetic studies of ferrihydrite nanoparticles. United States: N. p., 2000. Web. doi:10.1103/PhysRevB.61.3513.
Seehra, M S, Babu, V S, Manivannan, A, & Lynn, J W. Neutron scattering and magnetic studies of ferrihydrite nanoparticles. United States. doi:10.1103/PhysRevB.61.3513.
Seehra, M S, Babu, V S, Manivannan, A, and Lynn, J W. Tue . "Neutron scattering and magnetic studies of ferrihydrite nanoparticles". United States. doi:10.1103/PhysRevB.61.3513.
@article{osti_20215333,
title = {Neutron scattering and magnetic studies of ferrihydrite nanoparticles},
author = {Seehra, M S and Babu, V S and Manivannan, A and Lynn, J W},
abstractNote = {Magnetic properties of two-line ferrihydrite (FeOOD{center_dot}nD{sub 2}O) nanoparticles with an average size {approx_equal}4 nm are investigated using neutron scattering and magnetometry. Comparison of the neutron scattering and x-ray diffraction patterns identifies the (002) peak at Q=1.3 Aa{sup -1} as predominantly magnetic. The intensity of this peak, measured from 10 to 450 K, decreases almost linearly with temperature until 350 K, becoming temperature independent above 350 K. From this, T{sub N}{approx_equal}350 K is identified to be the ordering temperature of the core spins of the nanoparticles. The width of the line is temperature independent, yielding a magnetic coherence length(approx =)particle size. The temperature variations (5-300 K) of the initial susceptibility {chi} for the field-cooled (FC) and zero-field-cooled (ZFC) cases yield a peak at T{sub p}(m){approx_equal}65 K, below which {chi}(FC)>{chi}(ZFC). For T>T{sub p}(m), the variation of {chi}{sup -1} vs T is analyzed in terms of the model of El-Hilo et al., involving particle-size distribution and interparticle interactions, and substantial interparticle interactions are inferred. Following the observations in ferritin, the field dependence of the magnetization M for T>T{sub p}(m) is analyzed in terms of the modified Langevin variation: M=M{sub o}L({mu}{sub p}H/kT)+{chi}{sub a}H, where {mu}{sub p} is the magnetic moment/particle. The fit at 100 K yields {mu}{sub p}{approx_equal}250 {mu}{sub B}, consistent with the theoretical estimates based on uncompensated surface spins of Fe{sup 3+}. (c) 2000 The American Physical Society.},
doi = {10.1103/PhysRevB.61.3513},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
issn = {1098-0121},
number = 5,
volume = 61,
place = {United States},
year = {2000},
month = {2}
}