Neutron scattering and magnetic studies of ferrihydrite nanoparticles

Journal Article · Tue Feb 01 00:00:00 EST 2000 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.61.3513· OSTI ID:20215333

Seehra, M S ^[1]; Babu, V S ^[1]; Manivannan, A ^[1]; Lynn, J W ^[2]

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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)

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.

• OSTI ID: 20215333
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 61, Issue 5; Other Information: PBD: 1 Feb 2000; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

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