Magnetic and Mössbauer studies of Co adsorbed γ-Fe2O3

Okada, Takuya; Sekizawa, Hisashi; Ambe, F.; Ambe, S.; Yamadaya, T.

doi:10.1016/0304-8853(83)90732-1

Cited by 32 publications

(16 citation statements)

References 2 publications

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“…8 Considering surface vs in-volume effects, most studies are devoted to ferrimagnetic nanoparticles, where unlike in AF NPs, surface is the origin of a reduction in the magnetic moment. These studies are not unanimous with some authors claiming the preferential surface canting 9,10 in disagreement with others where finite-size/in-volume effects are observed. 11,12 Studies comparing surfactant-coated particles with uncoated ones show that the magnetic properties are greatly affected by the surfactant-particle interaction, suggesting the surface nature of this phenomena.…”

Section: Introductioncontrasting

confidence: 53%

Remanent magnetization in CoO antiferromagnetic nanoparticles

et al. 2010

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We report a study on the remanent magnetization M r induced by field cooling across the ordering temperature T N in antiferromagnetic CoO nanoparticles with different sizes. The nanoparticles are composed by a structurally and magnetically ordered core and a structurally ordered and magnetically disordered shell with a thickness of about 2 nm. The ordered core has cell parameters, moments direction, and modulus similar to those of bulk CoO. M r is shown to be proportional to the cooling field H cool . The low-temperature saturation values of M r ͓M r ͑0͔͒ in the CoO nanoparticles are about two orders of magnitude higher than those found for bulk CoO. M r / M r ͑0͒ of CoO nanoparticles scales with temperature in a single curve, independently on the magnitude of H cool and on nanoparticles size, except for temperatures near to T N since T N is size dependent.

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Section: Introductioncontrasting

confidence: 53%

Remanent magnetization in CoO antiferromagnetic nanoparticles

et al. 2010

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“…Whereas M s (D,T a ) of FM nanocrystals decreases with dropping D, remarkable reductions of M s (D,T a ) of Fe-Ni invar alloy (< 40 nm) [144], Ni thin films [145,146] and Fe, Co and Ni nanoparticles [147] Since then, the problem has been revisited with arguments in favor of a surface origin [157] and in favor of a finite size effect [158]. However, no clear conclusions about it have been given yet [159].…”

Section: Magnetizationmentioning

confidence: 99%

Size Dependence of Structures and Properties of Magnetic Materials

Jiang¹,

Lang²

2007

TONANOJ

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Due to the involvement of high portion of atomic coordination imperfection in surfaces and interfaces, the properties of magnetic nanocrystals dramatically differ from that of the corresponding bulk counterparts, which have led to a surge in both experimental and theoretical investigations in the past decades. This review summarizes the studies for these size-dependent magnetic properties, and additional thermal or phase stabilities, and mechanical properties. To interpret the above phenomena, a thermodynamic model for the size dependence and interface dependences of these properties is described, which is based on Lindemann s criterion for melting, Mott s expression for the vibrational melting entropy, and Shi s model for the size-dependent melting temperature. The model without any adjustable parameter is confirmed by a large number of experimental results, and helps us to understand the structures and properties of the magnetic nanocrystals. Moreover, other theoretical works on the above properties are also mentioned and commented.

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“…In more recent works devoted to the study of different ferrimagnetic oxides-␥-Fe 2 O 3 , NiFe 2 O 4 , CoFe 2 O 4 , CuFe 2 O 4 , in the form of nanometric particles [1][2][3][4][5] -a random spin canting at the surface, caused by competing antiferromagnetic ͑AF͒ interactions, was observed by Mössbauer spectroscopy, 2 polarized 4 and inelastic 6 neutron scattering, and ferromagnetic ͑FM͒ resonance. 7 The origin of this noncollinear arrangement of the spins was discussed by several authors supporting the surface 2,[8][9][10] or the finite-size explanations, [11][12][13][14][15] but up to the moment no clear conclusions have been established.…”

Section: Introductionmentioning

confidence: 99%

Finite-size and surface effects in maghemite nanoparticles: Monte Carlo simulations

2001

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Finite-size and surface effects in fine particle systems are investigated by Monte Carlo simulation of a model of a ␥-Fe 2 O 3 ͑maghemite͒ single particle. Periodic boundary conditions for a large enough system have been used to simulate the bulk properties and the results compared with those for a spherical shaped particle with free boundaries to evidence the role played by the surface on the anomalous magnetic properties displayed by these systems at low temperatures. Several outcomes of the model are in qualitative agreement with the experimental findings. A reduction of the magnetic ordering temperature, spontaneous magnetization, and coercive field is observed as the particle size is decreased. Moreover, the hysteresis loops become elongated with high values of the differential susceptibility, resembling those from frustrated or disordered systems. These facts are a consequence of the formation of a surface layer with higher degree of magnetic disorder than the core, which, for small sizes, dominates the magnetization processes of the particle. However, in contradiction with the assumptions of some authors, our model does not predict the freezing of the surface layer into a spin-glass-like state. The results indicate that magnetic disorder at the surface simply facilitates the thermal demagnetization of the particle at zero field, while the magnetization is increased at moderate fields, since surface disorder diminishes ferrimagnetic correlations within the particle. The change in shape of the hysteresis loops with the particle size demonstrates that the reversal mode is strongly influenced by the reduced atomic coordination and disorder at the surface.

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Magnetic and Mössbauer studies of Co adsorbed γ-Fe2O3

Cited by 32 publications

References 2 publications

Remanent magnetization in CoO antiferromagnetic nanoparticles

Remanent magnetization in CoO antiferromagnetic nanoparticles

Size Dependence of Structures and Properties of Magnetic Materials

Finite-size and surface effects in maghemite nanoparticles: Monte Carlo simulations

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