Nano Archive

Nanocrystalline nickel ferrite, NiFe2O4: Mechanosynthesis, nonequilibrium cation distribution, canted spin arrangement, and magnetic behavior

Sepelak, Vladimir and Bergmann, Ingo and Feldhoff, Armin and Heitjans, Paul and Krumeich, Frank and Menzel, Dirk and Litterst, Fred J. and Campbell, Stewart J. and Becker, Klaus D. (2007) Nanocrystalline nickel ferrite, NiFe2O4: Mechanosynthesis, nonequilibrium cation distribution, canted spin arrangement, and magnetic behavior. JOURNAL OF PHYSICAL CHEMISTRY C, 111 (13). pp. 5026-5033.

Full text is not hosted in this archive but may be available via the Official URL, or by requesting a copy from the corresponding author.

Official URL: http://dx.doi.org/10.1021/jp067620s

Abstract

Nickel ferrite (NiFe2O4) nanoparticles with an average crystallite size of about 8.6 nm were prepared by mechanochemical synthesis (mechanosynthesis). In-field Mossbauer spectroscopy and high-resolution TEM studies revealed a nonuniform structure of mechanosynthesized NiFe2O4 nanoparticles consisting of an ordered core surrounded by a disordered grain boundary (surface) region. The inner core of a NiFe2O4 nanoparticle is considered to possess a fully inverse spinel structure with a Neel-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 Mossbauer experiments. On heating above 673 K, the mechanosynthesized NiFe2O4 relaxes to a structural and magnetic state that is similar to the bulk one.

Item Type:Article
Subjects:Material Science > Nanofabrication processes and tools
Material Science > Nanochemistry
Material Science > Nanostructured materials
ID Code:2664
Deposited By:Anuj Seth
Deposited On:09 Jan 2009 10:35
Last Modified:20 Jan 2009 11:12

Repository Staff Only: item control page