1. Particle Size Dependence of Magnetic Properties in Zinc Ferrite Nanoparticles
Jun Hee Cho1, Sang Gil Ko1, Yang kyu Ahn1, Eun Jung Choi2 * 1Department of Nanochemistry & Biochemistry,
Konyang University, Nonsan, Chungnam, Korea
2Department of opthalmic Optics, Konyang University
Daejeon , Korea

2. Experimental Procedure
1. Synthesis : Microemulsion method
2. X-ray diffraction pattern (XRD)
3. Superconducting quantum interference device (SQUID)
4. Mössbauer spectroscopy
DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY

3. Synthesis of nanosize ZnFe2O4 particles
Metal Ion Aqueous Solution
(ZnCl2/FeCl3 0.1M)
Drying  & Aging (600K)
Decantation & Washing
with Solvent & Aalcohol
Coprecipitation
(Zinc-Iron Hydrixide
Carbonate Particles with
Surfactant)
Mixing & Stirring
 at R.T.
Nanosize Zn-Ferrite Particles
Alkali Aqueous Solution
(Na2CO3 0.2M)
Microemulsions
0.2M AOT in iso-Octane
Water drops in oil
MFe(OH)n
Exchange of water content
Precipitation
&
Particle growth
Surfactant
stabilized particle
DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY

4. X-ray diffraction pattern of ZnFe2O4 nanoprticles
1. Cubic spinel structure
2. Lattice parameter α0=8.43Å
3. Cation distribution
   (Zn0.72Fe0.28)[Zn0.28Fe1.78]O4
DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY

5. Magnetic hysteresis curve of ZnFe2O4 nanoparticles5K
100K
200K
300K
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6. Mössbauer spectrum at various temperatures
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7. Mössbauer spectrum at various temperatures
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8. Cation distribution DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY
(Zn1-xFex)[ZnxFe2-x]O4
Area ratio of the A and B subspectra for the above distribution
Where ∱A and ∱B represent the recoil-free fraction of A and B site
Fe ions, respectively.
Recoil Free Fraction ∱
Where ER is the recoil energy of 57Fe for the 14.4 keV gamma ray.
θ and kB represent the Debye temperature and the Boltzmann constant.
(Zn0.72Fe0.28)[Zn0.28Fe1.72]O4
DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY

9. Superparamagnetic Broadening from
the distribution of quadrupole splittings
Mössbauer line shift EQ from the pure magnetic lines due to the quadrupole interaction
where θ and Ф are the polar and azimuth angles of the magnetic hyperfine field vector relative to the principal axes of the electric-field-gradient tensor.
On assuming that the maximum electric field gradient q and the asymmetry parameter ŋ are independent of θ and Ф , the average value of EQ taken over all directions vanishes, i.e.
DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY

10. DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY
The line broadening from this random distribution is not zero: that is,
 Another source of broadening can be estimated from the linewidth, 0.42 mm/s, of the quadrupole dooublet above the Curie temperature. In view of the 0.25 mm/s linewidth of an iron foil, a line broadening of 0.17 mm/s of the doublet is the result of distributions of the isomer shift and magnitudes of q and ŋ in addition to the thickness effect of the absorber. Thus, the combined broadening from distribution of quadrupole splitting and isomer shift can not be negligible.
DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY

11. Conclusions DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY
▶ Nanosize ZnFe2O4 particle have been synthesized using
    microemulsion method.
▶ Cubic mixed spinel structure
▶ the lattice constant :  α0=8.43Å
▶ Combined broadening from distribution of quadrupole
splitting and isomer shift is not negligible.
▶ Cation distribution (Zn0.72Fe0.29)[Co0.29Fe1.72]O4
▶ Neel temperature : 120 K
DEPARTMENT OF OPTHALMIC OPTICS KONYANG UNIVERSITY