First-Principles Analysis of Cation Diffusion in Mixed Metal Ferrite Spinels

Muhich, Christopher L.; Aston, Victoria J.; Trottier, Ryan M.; Weimer, Alan W.; Musgrave, Charles B.

doi:10.1021/acs.chemmater.5b03911

Cited by 83 publications

(54 citation statements)

References 60 publications

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“…(Figure a) does not match with our experimentally obtained data especially at lower magnetic field. For low magnetic field correction, a tan hyperbolic function of H is often found suitable to explain the nature of MR curves and matches with our observed experimental result

m true(H true) = α \tanh true(\frac{H}{H_{0}} true) + true(1 - α true) \exp true(- \frac{k}{\sqrt{H}} true)

…”

Section: Resultssupporting

confidence: 89%

“…In octahedral site of spinel Fe 3 O 4 , both Fe 2+ and Fe 3+ coexists and the spin down t 2g electron in Fe 2+ hops between Fe 2+ and Fe 3+ . This itinerant electron of Fe 2+/3+ is responsible for the semi‐metallic nature of Fe 3 O 4 . For CoFe 2 O 4 , Co 2+ replaces Fe 2+ in the octahedral site, therefore, the hopping of t 2g electron does not occur and CoFe 2 O 4 becomes an insulator .…”

Section: Resultsmentioning

confidence: 99%

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Engineering Magnetic and Tunneling Magnetoresistance Properties of Co_xFe_3−xO₄ Nanorods

Mitra

Mohapatra

Sharma

et al. 2017

Physica Status Solidi (a)

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A simple cation exchange reaction has been adapted to produce the CoxFe3−xO4 nanorods with different concentration of Co. The substitution of Fe2+ with Co2+ ions increase the magnetocrystalline anisotropy and coercivity of pristine superparamagnetic Fe3O4 nanorods. Atomic concentration of 5–11% of Co2+ in Fe3O4 nanorods renders coercivity of 300–460 Oe at room temperature and 2200–4050 Oe at 10 K. Hydrocarbon long‐chain amine (oleylamine) functionalized nanorod assemblies form a multiple tunnel junction, where organic amine monolayers act as insulating tunnel barriers. CoxFe3−xO4 nanorods show a magnetoresistance switching behavior at room temperature and the switching field is consistent with the magnetic coercivity. A 14–15% TMR is recorded at room temperature in CoxFe3−xO4 nanorod assemblies, which increases to 23–26% at 150 K at a magnetic field of ±2 T. The calculated spin polarization for Co0.33Fe2.67O4 nanorods at room temperature is 52%. A similar spin polarization and TMR as Fe3O4 in Co‐doped Fe3O4 nanorod assemblies is obtained. Thus, controlled doping of Co ions engineers the coercivity and remanence of the “super‐paramagnetic” Fe3O4 without hindering their TMR performances, which could be very useful for memory devices.

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m true(H true) = α \tanh true(\frac{H}{H_{0}} true) + true(1 - α true) \exp true(- \frac{k}{\sqrt{H}} true)

…”

Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Engineering Magnetic and Tunneling Magnetoresistance Properties of Co_xFe_3−xO₄ Nanorods

Mitra

Mohapatra

Sharma

et al. 2017

Physica Status Solidi (a)

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show abstract

“…In Figure 6b, the electronic structure of Fe was surprisingly unvaried despite the difference of occupied sites of Fe. The crystal field diagrams of Fe 3+ (Oh) , Fe 3+ (Td) , and Co 2+ (Td) were in a high-spin arrangement, [47] except for that of Co 3+ (Oh) with a low-spin arrangement. The crystal field diagrams of Fe 3+ (Oh) , Fe 3+ (Td) , and Co 2+ (Td) were in a high-spin arrangement, [47] except for that of Co 3+ (Oh) with a low-spin arrangement.…”

Section: Resultsmentioning

confidence: 94%

Unraveling Geometrical Site Confinement in Highly Efficient Iron‐Doped Electrocatalysts toward Oxygen Evolution Reaction

Hung

Hsu

Chang

et al. 2017

Advanced Energy Materials

132

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to develop OER electrocatalysts with a low overpotential in order to scale down the energy expenditure of water electrolysis.To date, noble metal oxides, such as iridium oxide and ruthenium oxide, are regarded as the benchmarked OER electrocatalysts, [10][11][12][13] but their scarcity and high cost hinder them from the wide utilization. [14] For these reasons, it is of the essence to explore earth-abundant substances showing comparable performance as costly noble-metal electrocatalysts. Recently, earth-abundant transition-metalbased materials exhibited high performance and superb stability toward OER, especially for the cobalt and nickel-based oxides/nonoxides. [15][16][17][18][19][20][21][22] Furthermore, various metal dopants would greatly affect the activities and intrinsic attributes. For example, tungsten, chromium, iron, and zinc-doping have been discovered to improve the activities in contrast to pristine metal oxides owing to the optimization of adsorption energy for surface intermediates or the increment of roughness factor. [23][24][25][26][27][28][29] Interestingly, among these elements, iron can commonly perform significant enhancement in catalytic activities toward oxygen evolution reaction as compared to other elements. [30,31] Boettcher's group proposed that Fe ions granted the catalytic activities while Co ions acted as the conductive oxides to transport the charge carriers in an Fe-Co metal oxide system. [32] Friebel et al. conducted a series of operando experiments and calculations to demonstrate that Fe ions in Ni 1-x Fe x OOH system would alter the adsorption energies of OER intermediates over the electrocatalytic surface and thus reduce the overpotential of OER, whereas the formation of low-activity FeOOH declined the resulting activities in the cases of higher Fe content. [33] Howbeit, the behavior of iron based on the material insight was not elaborated. Toward this end, it is crucial to establish the direct relationship between the material characteristics and the catalytic activities.Recently, we reported that the geometrical sites in spinel cobalt oxide served distinct functions. In the case of Co 3 O 4 , the cobalt ions in octahedral site (Co 3+ (Oh) ) contributed to surface double layer capacitance while those in tetrahedral site (Co 2+ (Td) ) were able to adsorb oxygen ions onto the surface for being the active species. [34,35] It suggested that even for the identical Introduction of iron in various catalytic systems has served a crucial function to significantly enhance the catalytic activity toward oxygen evolution reaction (OER), but the relationship between material properties and catalysis is still elusive. In this study, by regulating the distinctive geometric sites in spinel, Fe occupies the octahedral sites (Fe 3+ (Oh) ) and confines Co to the tetrahedral site (Co 2+ (Td) ), resulting in a strikingly high activity (η j = 10 mA cm −2 = 229 mV and η j = 100 mA cm −2 = 281 mV). Further enrichment of Fe ions would occupy the tetrahedral sites to decline the amount of Co 2+ (Td) a...

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“…A similar trend has also been reported for spinel-type ferrite compounds. 25 A recent computational study has shown that the energy barrier of A-site cation diffusion in (Ba,Sr)ZrO 3 is dependent on the intermediate configurations during diffusion of the A-cation to the next A-site vacancy and is inversely proportional to the unit cell volume. 13 This can be attributed to Coulomb's repulsion of positively charged species either A-A or A-B in ABO 3 .…”

Section: Ba Xmentioning

confidence: 99%

134Ba diffusion in polycrystalline BaMO3 (M = Ti, Zr, Ce)

et al. 2017

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Cation diffusion in functional oxide materials is of fundamental interest, particularly in relation to interdiffusion of cations in thin film heterostructures and chemical stability of materials in high temperature electrochemical devices. Here we report on 134Ba tracer diffusion in polycrystalline BaMO3 (M = Ti, Zr, Ce) materials. The dense BaMO3 ceramics were prepared by solid state sintering, and thin films of 134BaO were deposited on the polished pellets by drop casting of an aqueous solution containing the Ba-tracer. The samples were subjected to thermal annealing and the resulting isotope distribution profiles were recorded by secondary ion mass spectrometry. The depth profiles exhibited two distinct regions reflecting lattice and grain boundary diffusion. The grain boundary diffusion was found to be 4-5 orders of magnitude faster than the lattice diffusion for all three materials. The temperature dependence of the lattice and grain boundary diffusion coefficients followed an Arrhenius type behaviour, and the activation energy and pre-exponential factor demonstrated a clear correlation with the size of the primitive unit cell of the three perovskites. Diffusion of Ba via Ba-vacancies was proposed as the most likely diffusion mechanism.

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First-Principles Analysis of Cation Diffusion in Mixed Metal Ferrite Spinels

Cited by 83 publications

References 60 publications

Engineering Magnetic and Tunneling Magnetoresistance Properties of Co_xFe_3−xO₄ Nanorods

Engineering Magnetic and Tunneling Magnetoresistance Properties of Co_xFe_3−xO₄ Nanorods

Unraveling Geometrical Site Confinement in Highly Efficient Iron‐Doped Electrocatalysts toward Oxygen Evolution Reaction

134Ba diffusion in polycrystalline BaMO3 (M = Ti, Zr, Ce)

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First-Principles Analysis of Cation Diffusion in Mixed Metal Ferrite Spinels

Cited by 83 publications

References 60 publications

Engineering Magnetic and Tunneling Magnetoresistance Properties of CoxFe3−xO4 Nanorods

Engineering Magnetic and Tunneling Magnetoresistance Properties of CoxFe3−xO4 Nanorods

Unraveling Geometrical Site Confinement in Highly Efficient Iron‐Doped Electrocatalysts toward Oxygen Evolution Reaction

134Ba diffusion in polycrystalline BaMO3 (M = Ti, Zr, Ce)

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Engineering Magnetic and Tunneling Magnetoresistance Properties of Co_xFe_3−xO₄ Nanorods

Engineering Magnetic and Tunneling Magnetoresistance Properties of Co_xFe_3−xO₄ Nanorods