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Title: Temperature-dependent structure of Tb-doped magnetite nanoparticles

High quality 5 nm cubic Tb-doped magnetite nanoparticles have been synthesized by a wet-chemical method to investigate tailoring of magnetic properties for imaging and biomedical applications. We show that the Tb is incorporated into the octahedral 3+ sites. High-angle annular dark-field microscopy shows that the dopant is well-distributed throughout the particle, and x-ray diffraction measurements show a small lattice parameter shift with the inclusion of a rare-earth dopant. Magnetization and x-ray magnetic circular dichroism data indicate that the Tb spins are unpolarized and weakly coupled to the iron spin lattice at room temperature, and begin to polarize and couple to the iron oxide lattice at temperatures below 50 K. Broadband ferromagnetic resonance measurements show no increase in magnetic damping at room temperature for Tb-doped nanoparticles relative to undoped nanoparticles, further confirming weak coupling between Fe and Tb spins at room temperature. The Gilbert damping constant, α, is remarkably low for the Tb-doped nanoparticles, with α = 0.024 ± 0.003. These nanoparticles, which have a large fixed moment, a large fluctuating moment and optically active rare-earth elements, are potential high-relaxivity T1 and T2 MRI agents with integrated optical signatures.
Authors:
; ; ; ; ; ;  [1] ;  [2] ;  [3] ;  [4]
  1. National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)
  2. Colorado State University, Fort Collins, Colorado 80523 (United States)
  3. Lawrence Berkeley National Laboratory, Advanced Light Source, Berkeley, California 94720 (United States)
  4. Department of Physics, Montana State University, Bozeman, Montana 59717 (United States)
Publication Date:
OSTI Identifier:
22412617
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; COUPLING; DOPED MATERIALS; FERROMAGNETIC RESONANCE; IRON; IRON OXIDES; LATTICE PARAMETERS; MAGNETIC CIRCULAR DICHROISM; MAGNETIC PROPERTIES; MAGNETITE; MAGNETIZATION; NANOPARTICLES; NMR IMAGING; RARE EARTHS; SPIN; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0273-0400 K; TERBIUM; X-RAY DIFFRACTION