Systematic analysis of structural and magnetic properties of spinel CoB<sub>2</sub>O<sub>4</sub>(B  =  Cr, Mn and Fe) compounds from their electronic structures

Das, Debashish; Biswas, Rajkumar; Ghosh, Subhradip

doi:10.1088/0953-8984/28/44/446001

Cited by 32 publications

(21 citation statements)

References 40 publications

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“…The two-body and three-body simulation results at the Co K-edge are listed in Table 3 and Table 4, respectively, those at the Fe K-edge are listed in Tables S2 and S3 (in Supplementary Materials). The atomic distances are in good agreement with the literature values for the inverse spinel structure [40,41,42,43,44]. Nevertheless, the coordination numbers (CNs) for both the standard and the nanodots are smaller than the theoretical values for the inverse spinel structure.…”

Section: Resultssupporting

confidence: 88%

“…From bottom to top, the spectra are as follows: the ion-loaded BCP template before UVO, after UVO, after UVO and TA at 200 °C, after UVO and TA at 400 °C, after UVO and TA at 600 °C, after UVO and TA at 600 then 950 °C, and the commercial CFO nano powder. The four vertical dashed lines in the Co K-edge FT spectra mark the peak positions for I: Co 1 –O and Co 2 –O, II: Co 2 ···M 2 , III: Co 2 ···M 1 , Co 1 ···M 2 , Co 1 ···O and Co 2 ···O and IV: Co 2 ···M 2 [40,41,42,43,44], where M represents Co or Fe, and the superscripts 1 and 2 represent respectively the tetrahedral site and the octahedral site (see Figure S1 in Supplemtary Materials) in the inverse spinel unit cell, respectively. At the Fe K-edge, the peak positions are I: Fe 1 –O and Fe 2 –O, II: Fe 2 ···M 2 , III: Fe 2 ···M 1 , Fe 1 ···M 2 , Fe 1 ···O and Fe 2 ···O and IV: Fe 2 ···M 2 [40,41,42,43,44].…”

Section: Resultsmentioning

confidence: 99%

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Chemical Solution Deposition of Ordered 2D Arrays of Room-Temperature Ferrimagnetic Cobalt Ferrite Nanodots

Varghese

Portale

et al. 2019

Polymers

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Over the past decades, the development of nano-scale electronic devices and high-density memory storage media has raised the demand for low-cost fabrication methods of two-dimensional (2D) arrays of magnetic nanostructures. Here, we present a chemical solution deposition methodology to produce 2D arrays of cobalt ferrite (CFO) nanodots on Si substrates. Using thin films of four different self-assembled block copolymers as templates, ordered arrays of nanodots with four different characteristic dimensions were fabricated. The dot sizes and their long-range arrangement were studied with scanning electron microscopy (SEM) and grazing incident small-angle X-ray scattering (GISAXS). The structural evolution during UV/ozone treatment and the following thermal annealing was investigated through monitoring the atomic arrangement with X-ray absorption fine structure spectroscopy (EXAFS) and checking the morphology at each preparation step. The preparation method presented here obtains array types that exhibit thicknesses less than 10 nm and blocking temperatures above room temperature (e.g., 312 K for 20 nm diameter dots). Control over the average dot size allows observing an increase of the blocking temperature with increasing dot diameter. The nanodots present promising properties for room temperature data storage, especially if a better control over their size distribution will be achieved in the future.

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Chemical Solution Deposition of Ordered 2D Arrays of Room-Temperature Ferrimagnetic Cobalt Ferrite Nanodots

Varghese

Portale

et al. 2019

Polymers

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“…The inverse spinel Fe2CoO4 structure is characterised by half of the octahedral (Oh) sites being occupied by Co 2+ cations and the other half of the octahedral sites and all of the tetrahedral (Td) sites being occupied by Fe 3+ cations (Figure 1a). After full relaxation of the bulk Fe2CoO4 unit cell, the lattice constant is determined to be a = 8.435 Å, which is in good agreement with experimental (a = 8.533 Å) and previous GGA+U (8.41−8.46 Å) values [28,29]. The optimised Co-O, FeOh-O, and FeTd-O bond lengths are calculated at 2.10 Å, 2.04 Å, and 1.90 Å, respectively, in close agreement with previous GGA+U predictions [30].…”

Section: Bulk Propertiessupporting

confidence: 86%

First-Principles Density Functional Theory Characterisation of the Adsorption Complexes of H3AsO3 on Cobalt Ferrite (Fe2CoO4) Surfaces

Lewis

Dzade

2021

Minerals

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The mobility of arsenic in aqueous systems can be controlled by its adsorption onto the surfaces of iron oxide minerals such as cobalt ferrite (Fe2CoO4). In this work, the adsorption energies, geometries, and vibrational properties of the most common form of As(III), arsenous acid (H3AsO3), onto the low-index (001), (110), and (111) surfaces of Fe2CoO4 have been investigated under dry and aqueous conditions using periodic density functional theory (DFT) calculations. The dry and hydroxylated surfaces of Fe2CoO4 steadily followed an order of increasing surface energy, and thus decreasing stability, of (001) < (111) < (110). Consequently, the favourability of H3AsO3 adsorption increased in the same order, favouring the least stable (110) surface. However, by analysis of the equilibrium crystal morphologies, this surface is unlikely to occur naturally. The surfaces were demonstrated to be further stabilised by the introduction of H2O/OH species, which coordinate the surface cations, providing a closer match to the bulk coordination of the surface species. The adsorption complexes of H3AsO3 on the hydroxylated Fe2CoO4 surfaces with the inclusion of explicit solvation molecules are found to be generally more stable than on the dry surfaces, demonstrating the importance of hydrogen-bonded interactions. Inner-sphere complexes involving bonds between the surface cations and molecular O atoms were strongly favoured over outer-sphere complexes. On the dry surfaces, deprotonated bidentate binuclear configurations were most thermodynamically favoured, whereas monodentate mononuclear configurations were typically more prevalent on the hydroxylated surfaces. Vibrational frequencies were analysed to ascertain the stabilities of the different adsorption complexes and to assign the As-O and O-H stretching modes of the adsorbed arsenic species. Our results highlight the importance of cobalt as a potential adsorbent for arsenic contaminated water treatment.

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“…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 . Controlled doping of Co 2+ in octahedral site does not replace Fe 2+ ions completely and thus electron conduction takes place.…”

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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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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Systematic analysis of structural and magnetic properties of spinel CoB₂O₄(B = Cr, Mn and Fe) compounds from their electronic structures

Cited by 32 publications

References 40 publications

Chemical Solution Deposition of Ordered 2D Arrays of Room-Temperature Ferrimagnetic Cobalt Ferrite Nanodots

Chemical Solution Deposition of Ordered 2D Arrays of Room-Temperature Ferrimagnetic Cobalt Ferrite Nanodots

First-Principles Density Functional Theory Characterisation of the Adsorption Complexes of H3AsO3 on Cobalt Ferrite (Fe2CoO4) Surfaces

Engineering Magnetic and Tunneling Magnetoresistance Properties of Co_xFe_3−xO₄ Nanorods

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Systematic analysis of structural and magnetic properties of spinel CoB2O4(B = Cr, Mn and Fe) compounds from their electronic structures

Cited by 32 publications

References 40 publications

Chemical Solution Deposition of Ordered 2D Arrays of Room-Temperature Ferrimagnetic Cobalt Ferrite Nanodots

Chemical Solution Deposition of Ordered 2D Arrays of Room-Temperature Ferrimagnetic Cobalt Ferrite Nanodots

First-Principles Density Functional Theory Characterisation of the Adsorption Complexes of H3AsO3 on Cobalt Ferrite (Fe2CoO4) Surfaces

Engineering Magnetic and Tunneling Magnetoresistance Properties of CoxFe3−xO4 Nanorods

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Systematic analysis of structural and magnetic properties of spinel CoB₂O₄(B = Cr, Mn and Fe) compounds from their electronic structures

Engineering Magnetic and Tunneling Magnetoresistance Properties of Co_xFe_3−xO₄ Nanorods