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Tang, Zuqi; Sorensen, C. M.; Klabunde, K. J.; Hadjipanayis, G. C.

doi:10.1103/physrevlett.67.3602

Cited by 334 publications

(205 citation statements)

References 11 publications

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“…In particular, it has been suggested that changes in the particle size, especially at the nanoscale, affect the magnetic properties as a consequence of a change in cation distribution. [1][2] However, other studies have pointed out that several spinels present the same cation distribution both in the nanophase and in the corresponding bulk samples indicating instead that the changes in the cation distribution can be associated to the formation of compounds retaining the spinel structure via the accommodation of vacancies within the lattice, that are difficult to detect since they have little effect on the X-ray diffraction patterns which are generally used to assess the crystalline structure of spinels. [2][3][4] The techniques of X-ray Absorption Near Edge Structure (XANES) and Extended Xray Absorption Fine Structure (EXAFS) were used in the latter studies to probe the local atomic environments of selected cations.…”

Section: Introductionmentioning

confidence: 99%

Cation distribution and vacancies in nickel cobaltite

Loche

Marras

Carta

et al. 2017

Phys. Chem. Chem. Phys.

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Samples of nickel cobaltite, a mixed oxide occurring in the spinel structure which is currently extensively investigated because of its prospective application as ferromagnetic, electrocatalytic, and cost-effective energy storage material were prepared in the form of nanocrystals stabilized in a highly porous silica aerogel and as unsupported nanoparticles.Nickel cobaltite nanocrystals with average size 4 nm are successfully grown for the first time into the silica aerogel provided that a controlled oxidation of the metal precursor phases is carried out, consisting in a reduction under H2 flow followed by mild oxidation in air. The investigation of the average oxidation state of the cations and of their distribution between the sites within the spinel structure, which is commonly described assuming the Ni cations are 2 only located in the octahedral sites, has been carried out by X-ray Absorption Spectroscopy providing evidence for the first time that the unsupported nickel cobaltite sample has a Ni:Co molar ratio higher than the nominal ratio of 1:2 and a larger than expected average overall oxidation state of the cobalt and nickel cations. This is achieved retaining the spinel structure, which accommodates vacancies to counterbalance the variation in oxidation state.3

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Section: Introductionmentioning

confidence: 99%

Cation distribution and vacancies in nickel cobaltite

Loche

Marras

Carta

et al. 2017

Phys. Chem. Chem. Phys.

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“…In the bulk form MnFe 2 O 4 is found to be 20% inverse with a stoichiometry of Mn 0. 8 where cations in brackets occupy octahedral sites. But a higher inversion up to 60% was reported in nanosized manganese ferrite [6].…”

Section: Introductionmentioning

confidence: 99%

Evidence for polaron conduction in nanostructured manganese ferrite

Gopalan¹,

Malini²,

Saravanan³

et al. 2008

J. Phys. D: Appl. Phys.

171

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Nanoparticles of manganese ferrite were prepared by the chemical co-precipitation technique. The dielectric parameters, namely, real and imaginary dielectric permittivity (ε and ε ), ac conductivity (σ ac ) and dielectric loss tangent (tan δ), were measured in the frequency range of 100 kHz-8 MHz at different temperatures. The variations of dielectric dispersion (ε ) and dielectric absorption (ε ) with frequency and temperature were also investigated. The variation of dielectric permittivity with frequency and temperature followed the Maxwell-Wagner model based on interfacial polarization in consonance with Koops phenomenological theory. The dielectric loss tangent and hence ε exhibited a relaxation at certain frequencies and at relatively higher temperatures. The dispersion of dielectric permittivity and broadening of the dielectric absorption suggest the possibility of a distribution of relaxation time and the existence of multiple equilibrium states in manganese ferrite. The activation energy estimated from the dielectric relaxation is found to be high and is characteristic of polaron conduction in the nanosized manganese ferrite. The ac conductivity followed a power law dependence σ ac = Bω n typical of charge transport assisted by a hopping or tunnelling process. The observed minimum in the temperature dependence of the frequency exponent n strongly suggests that tunnelling of the large polarons is the dominant transport process.

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“…Other low-dimensional nanocrystals, i.e. Ni nanorods [109,110] and nanoparticles [110,111], Gd [112], Fe 3 O 4 [113], and MnFe 2 O 4 [114] nanoparticles have been studied. Their structures and properties are determined by various techniques like magnetometry, spin-polarized photoemission, the magneto-optical Kerr effect, and acsusceptometry experiments, as well as more improved methods such as the ferromagnetic resonance, the conversionelectron Mössbauer spectroscopy, X-ray magnetic circular dichroism, the resonance magnetic X-ray spectroscopy, the magnetic force microscopy, etc.…”

Section: Experiments Resultsmentioning

confidence: 99%

“…This interesting result shows that for these alloys, algebria mean value has little error in comparison with the real value due to the similarity of elements consisting the alloys. [122] and MnFe 2 O 4 [114] are given in Fig. (4d).…”

Section: Verification Of T C (D) Functionmentioning

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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Size-dependent Curie temperature in nanoscaleMnFe2O4particles

Cited by 334 publications

References 11 publications

Cation distribution and vacancies in nickel cobaltite

Cation distribution and vacancies in nickel cobaltite

Evidence for polaron conduction in nanostructured manganese ferrite

Size Dependence of Structures and Properties of Magnetic Materials

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