Conversion of Worm-Shaped Antiferromagnetic Hematite to Ferrimagnetic Spherical Barium-Ferrite Nanoparticles for Particulate Recording Media

Jalli, Jeevan; Hong, Yang‐Ki; Lee, Jaejin; Abo, Gavin S.; Park, Jihoon; Lane, Alan M.; Kim, Seong‐Gon; Erwin, S. C.

doi:10.1109/lmag.2010.2087315

Cited by 13 publications

(6 citation statements)

References 19 publications

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“…The results manifest that the BaO doping in the NiZnCo ferrite leads to the formation of BaFe 2 O 4 phase at the grain‐boundary regions. BaFe 2 O 4 is a common intermediate phase or secondary phase in barium‐related ferrite materials like barium hexaferrites . For the present study, the BaFe 2 O 4 was supposed to grow at the early stage of the sintering procedure, through the reaction of the added BaO with slight diffused Fe 3+ , due to its relatively low formation temperature.…”

Section: Resultsmentioning

confidence: 99%

“…Second, the elemental composition for the Ba-rich grains is investigated through EDS spot analysis, as illustrated in Figure 4C. As a result, the Ba-rich grains are determined to be mainly composed of Ba, Fe, and O elements while almost none of Ni, Zn, and Co elements (no measurable Ni, Zn, and Co elemental content above the reliable detection limits of the instrument 25,26 For the present study, the BaFe 2 O 4 was supposed to grow at the early stage of the sintering procedure, through the reaction of the added BaO with slight diffused Fe 3+ , due to its relatively low formation temperature. For polycrystalline ceramic materials, it is known that the grain growth occurs with the processes of grain-boundary motion and diffusion actuated by the thermal energy in sintering.…”

Section: Phase Identification and Microstructurementioning

confidence: 99%

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Low loss and tailored high‐frequency performances of BaO‐doped NiZnCo magneto‐dielectric ferrites

Zheng

Feng

et al. 2019

J Am Ceram Soc

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Spinel ferrite ceramics of nominal composition Ni0.5Zn0.3Co0.2Fe2O4 (NiZnCo) with various BaO doping were successfully synthesized for applications as novel high‐frequency magneto‐dielectric materials. The influences of BaO doping on the crystal phase, density, microstructure, and magnetic and dielectric performances in the frequency range of 0.1 to 5 GHz were systematically studied. It is revealed that the doped Ba2+ ions aggregate to the grain‐boundary regions and lead to the formation of BaFe2O4 phase that significantly restrains the growth of NiZnCo ferrite grains. Correspondingly, permeability and permittivity are effectively tailored through the varied grain size and density, which is demonstrated by the magnetic circuit model and the modified effective medium theory proposed herein. As BaO content x = 1.2‐1.8 mol%, the NiZnCo ferrites reveal the excellent performance with almost equal values of μ′ and ε′, yielding a characteristic impedance to be nearly identical as that of free space over a wide frequency range of the VHF and UHF bands. Furthermore, the magnetic loss is effectively reduced at high frequencies, where the typical tan δμ at 0.5 GHz is decreased to ~0.043 with a reduction of up to 37% and the loss factor (tan δμ/μ′) is as low as ~0.006.

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Section: Resultsmentioning

confidence: 99%

Section: Phase Identification and Microstructurementioning

confidence: 99%

Low loss and tailored high‐frequency performances of BaO‐doped NiZnCo magneto‐dielectric ferrites

Zheng

Feng

et al. 2019

J Am Ceram Soc

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“…The total Gibbs free energy is the sum of the exchange w exch , anisotropy w ani , Zeeman w ext , and demagnetization w demag energies [17]: (1) , where (2) is the magnetic polarization as a function of space and time, A is the exchange constant, K 1 is the first magnetocrystalline anisotropy constant, a is the unit vector parallel to the easy axis, H ext is the external field, and H demag is the demagnetization field. The u x , u y , and u z are the direction cosines of the magnetization for the position vector u = u x i + u y j + u z k.…”

Section: Micromagnetic Computer Simulationmentioning

confidence: 99%

“…Spherical barium ferrite (S-BaFe: BaFe 12 O 19 ) particles have advantages over metal particles (MP) owing to a point-to-point contact for achieving high areal density for particulate recording media [1][2][3][4][5]. This is mainly because the MP requires a passivation layer that limits reduction of particle size due to low saturation magnetization and coercivity.…”

Section: Introductionmentioning

confidence: 99%

Shape Dependent Coercivity Simulation of a Spherical Barium Ferrite (S-BaFe) Particle with Uniaxial Anisotropy

Abo¹,

Hong²,

Jalli³

et al. 2012

Journal of Magnetics

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The coercivity of a single 27 nm-spherical barium ferrite (S-BaFe) particle was simulated using three models: 1) Gibbs free energy (GFE), 2) Landau-Lifshitz-Gilbert (LLG), and 3) Stoner-Wohlfarth (S-W). Spherically and hexagonally shaped particles were used in the GFE and LLG simulations to investigate coercivity with the different shape anisotropies. The effect of shape was not included in the S-W model. It was found that the models using a spherical shape resulted in a coercivity higher than the models using the hexagonal shape with both shapes having the same diameter. The coercivity estimated with the S-W model was approximately the same as that for the spherical-shape models, which indicates that spherical shape has no significant effect on the particle's coercivity at nanoscale.

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“…α-Fe 2 O 3 , the most stable phase of iron oxide has found applications in numerous fields including gas sensing (Hjiri, 2020), medicine (Rajendran et al, 2015;Naz et al, 2019), magnetic recording (Jalli et al, 2010), and PEC water splitting (Kim et al, 2013;Feng et al, 2020;Reddy et al, 2020). The use of α-Fe 2 O 3 as a photoanode for PEC water splitting has been broadly investigated in recent times because of its suitable properties such as low bandgap of ∼2.0 eV, stability in aqueous solution, availability, non-toxicity to the environment and low cost.…”

Section: Introductionmentioning

confidence: 99%

Effects of Film Thickness and Coating Techniques on the Photoelectrochemical Behaviour of Hematite Thin Films

2021

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In this research, three different sets of hematite (α-Fe2O3) films of various thicknesses were prepared using dip, spin, and combined dip/spin coating methods. α-Fe2O3 films of 450–500, 740–800 and 920–980 ± 30 nm thicknesses were prepared using each of the coating methods, and their photoelectrochemical (PEC) behaviour was investigated. Dip coated films produced the best photoresponse while the films prepared using the spin coating method yielded the least photocurrent values across films of different thicknesses. Maximum photocurrent densities of 34.6, 7.8, and 13.5 μA/cm2 V vs reversible hydrogen electrode (RHE) were obtained for the dip, spin and combined dip/spin coated films with a thickness of 740–800 ± 30 nm respectively. Improved crystallization, low charge transfer resistance at the α-Fe2O3/electrolyte interface, high surface states capacitance and the more negative flat band potential values obtained for dip coated films have been associated with the enhanced photocurrent response recorded for the films. The preferential crystal growth of spin coated films in the (104) plane associated with low electron mobility and the high resistance to charge transfer at the α-Fe2O3/electrolyte interface of the films is largely responsible for their low photoresponse. This study underscores the significance of simultaneously optimizing both coating techniques for film deposition and the film’s thickness in preparing nanostructured α-Fe2O3 films for PEC applications.

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Conversion of Worm-Shaped Antiferromagnetic Hematite to Ferrimagnetic Spherical Barium-Ferrite Nanoparticles for Particulate Recording Media

Cited by 13 publications

References 19 publications

Low loss and tailored high‐frequency performances of BaO‐doped NiZnCo magneto‐dielectric ferrites

Low loss and tailored high‐frequency performances of BaO‐doped NiZnCo magneto‐dielectric ferrites

Shape Dependent Coercivity Simulation of a Spherical Barium Ferrite (S-BaFe) Particle with Uniaxial Anisotropy

Effects of Film Thickness and Coating Techniques on the Photoelectrochemical Behaviour of Hematite Thin Films

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