Details
| Original language | English |
|---|---|
| Pages (from-to) | 5026-5033 |
| Number of pages | 8 |
| Journal | Journal of Physical Chemistry C |
| Volume | 111 |
| Issue number | 13 |
| Early online date | 9 Mar 2007 |
| Publication status | Published - 5 Apr 2007 |
Abstract
Nickel ferrite (NiFe2O4 nanoparticles with an average crystallite size of about 8.6 nm were prepared by mechanochemical synthesis (mechanosynthesis). In-field Mössbauer spectroscopy and high-resolution TEM studies revealed a nonuniform structure of mechanosynthesized NiFe 2O4 nanoparticles consisting of an ordered core surrounded by a disordered grain boundary (surface) region. The inner core of a NiFe 2O4 nanoparticle is considered to possess a fully inverse spinel structure with a Néel-type collinear spin alignment, whereas the surface shell is found to be structurally and magnetically disordered due to the nearly random distribution of cations and the canted spin arrangement. As a consequence of frustrated superexchange interactions in the surface shell, the mechanosynthesized NiFe2O4 exhibits a reduced nonsaturating magnetization, an enhanced coercivity, and a shifted hysteresis loop. The study also demonstrates that one can tailor the magnetic properties of mechanosynthesized NiFe2O4 particles by suitably controlling their size. The thickness of the surface shell of about 1 nm estimated from size-dependent magnetization measurements is found to be in good agreement with that obtained from high-resolution TEM and Mössbauer experiments. On heating above 673 K, the mechanosynthesized NiFe 2O4 relaxes to a structural and magnetic state that is similar to the bulk one.
ASJC Scopus subject areas
- Materials Science(all)
- Electronic, Optical and Magnetic Materials
- Energy(all)
- General Energy
- Chemistry(all)
- Physical and Theoretical Chemistry
- Materials Science(all)
- Surfaces, Coatings and Films
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In: Journal of Physical Chemistry C, Vol. 111, No. 13, 05.04.2007, p. 5026-5033.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Nanocrystalline nickel ferrite, NiFe2O4
T2 - Mechanosynthesis, nonequilibrium cation distribution, canted spin arrangement, and magnetic behavior
AU - Šepelák, Vladimir
AU - Bergmann, Ingo
AU - Feldhoff, Armin
AU - Heitjans, Paul
AU - Krumeich, Frank
AU - Menzel, Dirk
AU - Litterst, Fred J.
AU - Campbell, Stewart J.
AU - Becker, Klaus D.
PY - 2007/4/5
Y1 - 2007/4/5
N2 - Nickel ferrite (NiFe2O4 nanoparticles with an average crystallite size of about 8.6 nm were prepared by mechanochemical synthesis (mechanosynthesis). In-field Mössbauer spectroscopy and high-resolution TEM studies revealed a nonuniform structure of mechanosynthesized NiFe 2O4 nanoparticles consisting of an ordered core surrounded by a disordered grain boundary (surface) region. The inner core of a NiFe 2O4 nanoparticle is considered to possess a fully inverse spinel structure with a Néel-type collinear spin alignment, whereas the surface shell is found to be structurally and magnetically disordered due to the nearly random distribution of cations and the canted spin arrangement. As a consequence of frustrated superexchange interactions in the surface shell, the mechanosynthesized NiFe2O4 exhibits a reduced nonsaturating magnetization, an enhanced coercivity, and a shifted hysteresis loop. The study also demonstrates that one can tailor the magnetic properties of mechanosynthesized NiFe2O4 particles by suitably controlling their size. The thickness of the surface shell of about 1 nm estimated from size-dependent magnetization measurements is found to be in good agreement with that obtained from high-resolution TEM and Mössbauer experiments. On heating above 673 K, the mechanosynthesized NiFe 2O4 relaxes to a structural and magnetic state that is similar to the bulk one.
AB - Nickel ferrite (NiFe2O4 nanoparticles with an average crystallite size of about 8.6 nm were prepared by mechanochemical synthesis (mechanosynthesis). In-field Mössbauer spectroscopy and high-resolution TEM studies revealed a nonuniform structure of mechanosynthesized NiFe 2O4 nanoparticles consisting of an ordered core surrounded by a disordered grain boundary (surface) region. The inner core of a NiFe 2O4 nanoparticle is considered to possess a fully inverse spinel structure with a Néel-type collinear spin alignment, whereas the surface shell is found to be structurally and magnetically disordered due to the nearly random distribution of cations and the canted spin arrangement. As a consequence of frustrated superexchange interactions in the surface shell, the mechanosynthesized NiFe2O4 exhibits a reduced nonsaturating magnetization, an enhanced coercivity, and a shifted hysteresis loop. The study also demonstrates that one can tailor the magnetic properties of mechanosynthesized NiFe2O4 particles by suitably controlling their size. The thickness of the surface shell of about 1 nm estimated from size-dependent magnetization measurements is found to be in good agreement with that obtained from high-resolution TEM and Mössbauer experiments. On heating above 673 K, the mechanosynthesized NiFe 2O4 relaxes to a structural and magnetic state that is similar to the bulk one.
UR - http://www.scopus.com/inward/record.url?scp=34247517799&partnerID=8YFLogxK
U2 - 10.1021/jp067620s
DO - 10.1021/jp067620s
M3 - Article
AN - SCOPUS:34247517799
VL - 111
SP - 5026
EP - 5033
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 13
ER -