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Title: The magnetic transition in ε-Fe{sub 2}O{sub 3} nanoparticles: Magnetic properties and hyperfine interactions from Mössbauer spectroscopy

The nanoparticles of ε-Fe{sub 2}O{sub 3} enriched with {sup 57}Fe isotope in amorphous silica matrix were prepared by sol-gel technique starting from a single molecular precursor for both Fe{sub 2}O{sub 3} and silica. From the X-ray powder diffraction pattern ε-Fe{sub 2}O{sub 3} was identified as the major phase and α-Fe{sub 2}O{sub 3} and β-Fe{sub 2}O{sub 3} were observed as minor iron oxide phases. Using the log-normal distribution for fitting the experimental data from the TEM micrographs, the characteristic size of particles d{sub 0} ∼ 25 nm was derived. The rather high coercivity of ∼2.1 T at room temperature was confirmed for our nanoparticle system. From the dependences of magnetization on temperature a two-step magnetic transition spread between 100 K and 153 K was indicated. From the {sup 57}Fe Mössbauer spectra measured in the temperature range of 4.2–300 K, the hyperfine parameters for one tetrahedral and three octahedral sites of ε-Fe{sub 2}O{sub 3} structure were identified. The in-field spectra in the external magnetic fields up to 6 T were taken both above and below the indicated two-step magnetic transition. Their dependence on temperature and external magnetic field suggests that the first step in the temperature range of 153 K–130 K is related to the spin reorientation of the local magnetic momentsmore » in the magnetic sublattices and the second step in temperatures 130 K–100 K may be associated with the intermediate spin–high spin state transition of Fe{sup 3+} cation in the tetrahedral sublattice expressed in the change of the hyperfine magnetic field.« less
Authors:
; ; ; ;  [1] ; ; ;  [2] ;  [3]
  1. Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 18000 Prague (Czech Republic)
  2. Institute of Physics ASCR, v. v. i., Na Slovance 2, 18221 Prague (Czech Republic)
  3. Institute of Inorganic Chemistry of the ASCR, v. v. i., 25068 Husinec-Řež (Czech Republic)
Publication Date:
OSTI Identifier:
22410081
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 17; 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; 77 NANOSCIENCE AND NANOTECHNOLOGY; ABSORPTION SPECTROSCOPY; COERCIVE FORCE; FERRITES; HIGH SPIN STATES; IRON 57; IRON IONS; IRON OXIDES; MAGNETIC FIELDS; MAGNETIC MOMENTS; MAGNETIC PROPERTIES; MAGNETIZATION; MOESSBAUER EFFECT; NANOPARTICLES; SILICA; SOL-GEL PROCESS; SPIN; TEMPERATURE RANGE 0273-0400 K; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION