Single crystal synthesis and magnetic properties of Co2+-substituted and non-substituted magnetoplumbite-type Na–La ferrite

Waki, Takeshi; Takao, K.; Tabata, Yoshikazu; Nakamura, Hiroyuki

doi:10.1016/j.jssc.2019.121071

Cited by 9 publications

(5 citation statements)

References 18 publications

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“…However, comparison with inductively coupled plasma atomic emission spectrometry (ICP-AES), which gives the average value for the bulk sample, shows that the two analyses are in good agreement [33,34]. The high reliability of WDX has been demonstrated in many studies [28,31,[34][35][36][37][38][39][40][41]. In addition, WDX, which analyses a narrow spot where x-rays are irradiated, guarantees (iii) by sampling different parts of the crystal.…”

Section: Samplementioning

confidence: 99%

Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: ⁵⁹Co-NMR and DFT calculation study

Nakamura,

Ohta,

Kobayashi

et al. 2024

J. Phys. Mater.

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The La‒Co co-substituted magnetoplumbite-type (M-type) ferrites AFe12O19 (A = Ca, Sr and Ba, ion sizes Ca2+ < Sr2+ < Ba2+) with Co compositions around 0.2 have been subjected to 59Co-NMR. The results show that Co occupies the 4f1, 2a and 12k sites, and that the smaller the A ion, the more Co tends to occupy the 4f1 minority spin site, which is effective in enhancing both uniaxial anisotropy and magnetisation. First-principles total energy calculations based on density functional theory (DFT) of undoped AFe12O19 and a supercell (2×2×1 of the unit cell) in which 1/96 of Fe3+ is replaced by Co2+ were performed to predict the stable structure and Co occupancy sites. The results show that regardless of A, Co is most stable when it occupies the 4f1 site, followed by the 2a and 12k sites with energy differences on the order of 100 meV, and Co practically does not occupy the 2b and 4f2 sites. As the A ion becomes smaller, the energy difference when Co occupies each Fe site tends to increase, and the Co occupancy of the 4f1 site also increases. The site selectivity of Co can be roughly explained as a result of the difference in uniaxial strain along the c-axis associated with the difference in A. However, the influence of the A ion differs between the R and S blocks and the local strain also has a secondary effect on the Co distribution. Based on these results, the guidelines for improving the performance (anisotropy and magnetisation) of La‒Co co-substituted M-type ferrite magnets with a limited amount of Co can be summarised as follows: It is effective to select as small A ions as possible and to post-anneal at low temperature or cool slowly to concentrate Co at the 4f1 site in tetrahedral coordination.

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Section: Samplementioning

confidence: 99%

Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: ⁵⁹Co-NMR and DFT calculation study

Nakamura,

Ohta,

Kobayashi

et al. 2024

J. Phys. Mater.

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“…图 9 Na 2 O 助熔剂法制备的(a) La-SrM 和(b) La-Co SrM 单晶的难、易轴磁化曲线 [140] ；(c) [140,[142][143][144][145] (图中直线帮助判断 H A 增长趋势) Fig. 9.…”

Section: 单晶unclassified

“…9. Hard-and easy-axis magnetization curves of (a) La-SrM and (b) La-Co SrM single crystals prepared by the Na 2 O flux method [140] ; (c) Variation of the magnetic anisotropy field H A with the concentration of Co substitution for a series of samples of (Na/Ca-)La-Co substituted SrM at 5 K [140,[142][143][144][145] (the straight line helps to determine the trend of the H A growth)…”

Section: 单晶mentioning

confidence: 99%

“…量的易轴和难轴方向的磁化曲线 [140] 。在纯 SrM 中，两个方向都在分子磁矩为 20 .47 [108] ；而前文提到的 Na 2 O 助熔剂制备的单晶中，当 x=0.47 时，Co 替代量达到上限 y=0.27 [140] 。换句话说，La 和 Co 在常压制备条件下不平衡替代导致还原的 Fe 2+ 限制了 Co 2+ 的固溶度范围。Ueda 等 [142] 展所述，Küpferling 等 [147,148] 利用 La 对 SrM 进行了 0≤x≤1 范围内的替代，研究表明，La-SrM 的磁各向异性随 La 浓度和温度的改变表现出非线性变化，换句话说，在 La-SrM 中磁性离子 Fe 2+ 对 SrM 的磁各向异性作用具有复杂的浓度和温度依赖性。随后，Waki 等 [144,145] [39] 和 Co 替代的 Y 型铁氧体 SrFe 12 Co 2 O 22 [99] 、 W 型铁氧体 SrFe 16 Co 2 O 27 [98] [140] 中 La-Co…”

Section: 单晶unclassified

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Research progress of magnetic anisotropy enhancement mechanism of high-performance La-Co co-substituted M-type permanent magnet ferrites

Liu,

Wang,

et al. 2024

Acta Phys. Sin.

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La-Co co-substituted M-type ferrite,first reported at the end of the 20th century,has garnered continuous attention from researchers worldwide,serving as the cornerstone for high-performance permanent magnet ferrites.The unquenched orbital moments of Co2+ play a pivotal role in enhancing the uniaxial anisotropy of M-type ferrites.However,a comprehensive understanding of its microscopic mechanism remains elusive.In response to the escalating performance demands of ferrite materials,elucidating the mechanism behind magnetic anisotropy enhancement becomes imperative,alongside the quest for guiding principles facilitating the swift and cost-effective development of high-performance products.but its mechanism at the microscopic level has not been explained.This review encompasses a comprehensive analysis of various studies aimed at pinpointing the crystal sites of Co substitution within the lattice.These investigations including neutron diffraction,nuclear magnetic resonance,and Mössbauer spectroscopy delve into the fundamental origins underlying the enhancement of magnetic anisotropy,thereby furnishing valuable insights for material design strategies geared towards further augmenting the magnetic properties of permanent magnet ferrites.The exploration of Co-substitution sites has yielded noteworthy findings.Through meticulous examination and analysis,researchers have discerned the intricate interplay between Co ions and the lattice structure,shedding light on the mechanisms governing magnetic anisotropy enhancement.The current mainstream view is that Co ions tend to occupy more than one site,namely the 4f1,12k,and 2a sites,all of which are located within the spinel lattice.However,there have also been differing viewpoints,indicating that further exploration is needed to uncover the primary controlling factors influencing Co occupancy.Notably,the identification of specific Co substitution sites,especially the spin-down tetrahedron 4f1,has enabled targeted modifications,culminating in the fine-tuning of magnetic properties with remarkable precision.Furthermore,the reviewed studies underscore the pivotal role of crystallographic engineering in tailoring the magnetic characteristics of ferrite materials.By strategically manipulating Co substitution,researchers have harnessed the intrinsic properties of the lattice to amplify magnetic anisotropy,thereby unlocking new avenues for the advancement of permanent magnet ferrites.In conclusion,the collective findings outlined in this review herald a promising trajectory for the field of permanent magnet ferrites.Armed with a nuanced understanding of Co-substitution mechanisms,researchers are poised to chart novel pathways toward the development of next-generation ferrite materials boasting enhanced magnetic properties.

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“…Depending on the cation distribution on A and B sites, spinel ferrites display ferrimagnetic, antiferromagnetic, spin-glass, or paramagnetic behavior [1]. Among them, cobalt ferrite (CoFe 2 O 4 ) presents superparamagnetic behavior, high chemical stability, good mechanical hardness, moderate saturation magnetization (M S ), high coercivity (H C ), positive anisotropy constant (K), significant electrical resistance, low eddy current losses and low production costs [4][5][6][7]. CoFe 2 O 4 is a promising candidate for magnetic resonance imaging, drug delivery, tomography, tissue imaging ferrofluids, recording heads, magnetic sensors, microwave devices, magnetic refrigeration, catalysis, pigments, gas detectors, environmental remediation, etc.…”

Section: Introductionmentioning

confidence: 99%

Screening of Mono-, Di- and Trivalent Cationic Dopants for the Enhancement of Thermal Behavior, Kinetics, Structural, Morphological, Surface and Magnetic Properties of CoFe2O4-SiO2 Nanocomposites

Dippong

Levei

Petean

et al. 2023

IJMS

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CoFe2O4 is a promising functional material for various applications. The impact of doping with different cations (Ag+, Na+, Ca2+, Cd2+, and La3+) on the structural, thermal, kinetics, morphological, surface, and magnetic properties of CoFe2O4 nanoparticles synthesized via the sol-gel method and calcined at 400, 700 and 1000 °C is investigated. The thermal behavior of reactants during the synthesis process reveals the formation of metallic succinates up to 200 °C and their decomposition into metal oxides that further react and form the ferrites. The rate constant of succinates’ decomposition into ferrites calculated using the isotherms at 150, 200, 250, and 300 °C decrease with increasing temperature and depend on the doping cation. By calcination at low temperatures, single-phase ferrites with low crystallinity were observed, while at 1000 °C, the well-crystallized ferrites were accompanied by crystalline phases of the silica matrix (cristobalite and quartz). The atomic force microscopy images reveal spherical ferrite particles covered by an amorphous phase, the particle size, powder surface area, and coating thickness contingent on the doping ion and calcination temperature. The structural parameters estimated via X-ray diffraction (crystallite size, relative crystallinity, lattice parameter, unit cell volume, hopping length, density) and the magnetic parameters (saturation magnetization, remanent magnetization, magnetic moment per formula unit, coercivity, and anisotropy constant) depend on the doping ion and calcination temperature.

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Single crystal synthesis and magnetic properties of Co2+-substituted and non-substituted magnetoplumbite-type Na–La ferrite

Cited by 9 publications

References 18 publications

Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: ⁵⁹Co-NMR and DFT calculation study

Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: ⁵⁹Co-NMR and DFT calculation study

Research progress of magnetic anisotropy enhancement mechanism of high-performance La-Co co-substituted M-type permanent magnet ferrites

Screening of Mono-, Di- and Trivalent Cationic Dopants for the Enhancement of Thermal Behavior, Kinetics, Structural, Morphological, Surface and Magnetic Properties of CoFe2O4-SiO2 Nanocomposites

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Single crystal synthesis and magnetic properties of Co2+-substituted and non-substituted magnetoplumbite-type Na–La ferrite

Cited by 9 publications

References 18 publications

Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: 59Co-NMR and DFT calculation study

Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: 59Co-NMR and DFT calculation study

Research progress of magnetic anisotropy enhancement mechanism of high-performance La-Co co-substituted M-type permanent magnet ferrites

Screening of Mono-, Di- and Trivalent Cationic Dopants for the Enhancement of Thermal Behavior, Kinetics, Structural, Morphological, Surface and Magnetic Properties of CoFe2O4-SiO2 Nanocomposites

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Product

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Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: ⁵⁹Co-NMR and DFT calculation study

Site-selective cobalt substitution in La–Co co-substituted magnetoplumbite-type ferrites: ⁵⁹Co-NMR and DFT calculation study