Cation distribution in ZnFe2O4 fine particles studied by neutron powder diffraction

Kamiyama, Takashi; Haneda, K.; Satô, Toshihiko; Ikeda, Susumu; Asano, Hajime

doi:10.1016/0038-1098(92)90412-3

Cited by 157 publications

(87 citation statements)

References 13 publications

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“…When ZnFe 2 O 4 is prepared in the form of nanoparticles, it becomes ferrimagnetic due to a partial migration of Zn to the octahedral sites (Sato et al 1990;Kamiyama et al 1992;Jeyadevan et al 1994;Hamdeh et al 1997;Ammar et al 2004;Makovec and Drofenik 2008). The degree of inversion X for ZnFe 2 O 4 nanoparticles prepared by coprecipitation was determined to increase with decreasing particle size (Kamiyama et al 1992). Besides on the size, the degree of inversion also depends on the synthesis method (Ammar et al 2004;Tirosh et al 2006).…”

Section: Introductionmentioning

confidence: 99%

“…For example, ZnFe 2 O 4 shows paramagnetic behavior as bulk material due to its normal spinel structure, with Zn ions incorporated almost exclusively at tetrahedral sites. When ZnFe 2 O 4 is prepared in the form of nanoparticles, it becomes ferrimagnetic due to a partial migration of Zn to the octahedral sites (Sato et al 1990;Kamiyama et al 1992;Jeyadevan et al 1994;Hamdeh et al 1997;Ammar et al 2004;Makovec and Drofenik 2008). The degree of inversion X for ZnFe 2 O 4 nanoparticles prepared by coprecipitation was determined to increase with decreasing particle size (Kamiyama et al 1992).…”

Section: Introductionmentioning

confidence: 99%

“…In the case of nanoparticles, the structure can substantially deviate from the bulk. The flexibility of the crystal structure is particularly pronounced in the spinel ferrite nanoparticles (Sato et al 1990;Kamiyama et al 1992;Jeyadevan et al 1994;Hamdeh et al 1997;Ammar et al 2004;Makovec and Drofenik 2008;Carpenter et al 1999;Calvin et al 2002;Makovec et al 2009;Morrison et al 2004;Li et al 2000;Sivakumar et al 2007;Tirosh et al 2006). For example, ZnFe 2 O 4 shows paramagnetic behavior as bulk material due to its normal spinel structure, with Zn ions incorporated almost exclusively at tetrahedral sites.…”

Section: Introductionmentioning

confidence: 99%

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Influence of synthesis method on structural and magnetic properties of cobalt ferrite nanoparticles

et al. 2009

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The Co-ferrite nanoparticles having a relatively uniform size distribution around 8 nm were synthesized by three different methods. A simple coprecipitation from aqueous solutions and a coprecipitation in an environment of microemulsions are low temperature methods (50°C), whereas a thermal decomposition of organo-metallic complexes was performed at elevated temperature of 290°C. The X-ray diffractometry (XRD) showed spinel structure, and the high-resolution transmission electron microscopy (HRTEM) a good crystallinity of all the nanoparticles. Energy-dispersive X-ray spectroscopy (EDS) showed the composition close to stoichiometric (*CoFe 2 O 4 ) for both co-precipitated nanoparticles, whereas the nanoparticles prepared by the thermal decomposition were Co-deficient (*Co 0.6 Fe 2.4 O 4 ). The X-ray absorption near-edge structure (XANES) analysis showed Co valence of 2? in all the samples, Fe valence 3? in both coprecipitated samples, but average Fe valence of 2.7? in the sample synthesized by thermal decomposition. The variations in cation distribution within the spinel lattice were observed by structural refinement of Xray absorption fine structure (EXAFS). Like the bulk CoFe 2 O 4 , the nanoparticles synthesized at elevated temperature using thermal decomposition displayed inverse spinel structure with the Co ions occupying predominantly octahedral lattice sites, whereas coprecipitated samples showed considerable proportion of cobalt ions occupying tetrahedral sites (nearly 1/3 for the nanoparticles synthesized by co-precipitation from aqueous solutions and almost 1/4 for the nanoparticles synthesized in microemulsions). Magnetic measurements performed at room temperature and at 10 K were in good agreement with the nanoparticles' composition and the cation distribution in their structure. The presented study clearly shows that the distribution of the cations within the spinel lattice of the ferrite nanoparticles, and consequently their magnetic properties are strongly affected by the synthesis method used.Electronic supplementary material The online version of this article

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of synthesis method on structural and magnetic properties of cobalt ferrite nanoparticles

et al. 2009

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“…However, the surface atoms experience a different environment than those on the core of the particle. The surface magnetization is controlled by several parameters such as atomic vacancies, change in atomic coordination, dangling bonds, and lattice disorder [9][10][11][12][13][14][15][16][17][18][19][20][21]. These parameters result in disordered surface spins.…”

Section: Introductionmentioning

confidence: 99%

Investigating the Role of Shell Thickness and Field Cooling on Saturation Magnetization and Its Temperature Dependence in Fe3O4/γ-Fe2O3 Core/Shell Nanoparticles

2017

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Abstract:Understanding saturation magnetization and its behavior with particle size and temperature are essential for medical applications such magnetic hyperthermia. We report the effect of shell thickness and field cooling on the saturation magnetization and its behavior with temperature in Fe 3 O 4 /γ-Fe 2 O 3 core/shell nanoparticles of fixed core diameter (8 nm) and several shell thicknesses. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM, high-resolution transmission electron microscopy (HRTEM)) were used to investigate the phase and the morphology of the samples. Selected area electron diffraction (SAED) confirmed the core/shell structure and phases. Using a SQUID (San Diego, CA, USA), magnetic measurements were conducted in the temperature range of 2 to 300 K both under zero field-cooling (ZFC) and field-cooling (FC) protocols at several field-cooling values. In the ZFC state, considerable enhancement of saturation magnetization was obtained with the increase of shell thickness. After field cooling, we observed a drastic enhancement of the saturation magnetization in one sample up to 120 emu/g (50% larger than the bulk value). In both the FC and ZFC states, considerable deviations from the original Bloch's law were observed. These results are discussed and attributed to the existence of interface spin-glass clusters which are modified by the changes in the shell thickness and the field-cooling.

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“…For example, ZnFe 2 O 4 becomes ferrimagnetic, when prepared in the form of nanoparticles, because it adopts a partially inverted spinel structure (Sato et al 1990;Kamiyama et al 1992;Jeyadevan et al 1994;Hamdeh et al 1997;Ammar et al 2004). Using neutron powder diffraction, the degree of inversion X for ZnFe 2 O 4 nanoparticles prepared by co-precipitation was determined to increase with decreasing particle size from 0.108 at particle size 9.6 nm to 0.142 at particle size 2.9 nm (Kamiyama et al 1992). Besides on the particle size, the degree of inversion depends also on the preparation method (Hamdeh et al 1997;Ammar et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Structure of manganese zinc ferrite spinel nanoparticles prepared with co-precipitation in reversed microemulsions

et al. 2008

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The structure of Mn 0.5 Zn 0.5 Fe 2 O 4 spinel ferrite nanoparticles is studied as a function of their size and the experimental conditions of their synthesis using X-ray absorption spectroscopy. The nanoparticles of different sizes down to approximately 2 nm and with a narrow size distribution were synthesized using co-precipitation in reverse microemulsions. Simultaneous refinement of the X-ray absorption fine structure (EXAFS) of three constituting metals shows a migration of Mn and Zn ions to the octahedral site of the spinel lattice compensated by the corresponding migration of the Fe ions. To a smaller extent, Mn ions switch the occupation site already in bulk and in larger nanoparticles, while a sporadic migration of Zn is detected only in the nanoparticles with sizes below approximately 5 nm. X-ray absorption near edge structure (XANES) reveals considerable variations in the position of the Mn K edge, suggesting the average Mn valence in the nanoparticles to be higher than 3?. Annealing at 500°C relaxes the structure of as-synthesized nanoparticles toward the structure of the ceramic bulk standard.

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Cation distribution in ZnFe2O4 fine particles studied by neutron powder diffraction

Cited by 157 publications

References 13 publications

Influence of synthesis method on structural and magnetic properties of cobalt ferrite nanoparticles

Influence of synthesis method on structural and magnetic properties of cobalt ferrite nanoparticles

Investigating the Role of Shell Thickness and Field Cooling on Saturation Magnetization and Its Temperature Dependence in Fe3O4/γ-Fe2O3 Core/Shell Nanoparticles

Structure of manganese zinc ferrite spinel nanoparticles prepared with co-precipitation in reversed microemulsions

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