Hexagonal ferrites of X-, W-, and M-type in the system Sr–Fe–O: A comparative study

Töpfer, J.; Seifert, Daniela; Breton, Jean‐Marie Le; Langenhorst, F.; Chlan, V.; Kouřil, Karel; Štěpánková, H.

doi:10.1016/j.jssc.2015.02.007

Cited by 40 publications

(18 citation statements)

References 27 publications

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“…Furthermore, Co substitutions at the 4f 1 site were suggested from ND 11 , NMR 3 and X-ray magnetic circular dichroism (XMCD) 10 measurements, while another NMR research 12 suggested a different possibility of simultaneous occupation of the 4f 1 and 4f 2 sites. Given that the assignments of 57 Fe Mössbauer spectra 3,4,9 have been confirmed by recent first-principle calculations 13,14 by using the density functional theory, the discrepancies in the possible Co substitution sites may not be caused by incorrect assignments of Fe sites, but possibly by differences in chemical compositions, sample shapes and/or Oxygen atoms, which are at the corner of each polyhedron, are omitted for clarity. Each iron atom is located at the center of a polyhedron.…”

Section: Introductionmentioning

confidence: 84%

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Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite: Fe57 and Co59 nuclear magnetic resonance studies

et al. 2018

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To specify preferential occupation sites of Co substituents and to clarify charge and spin states of Co ions in (La, Co)-cosubstituted hexagonal magnetoplumbite-type (M-type) Sr ferrite Sr1−xLaxFe12−yCoyO19 (x, y ≤ 0.4), 57 Fe and 59 Co nuclear magnetic resonance (NMR) spectra are measured under zero and external magnetic fields using powdered and single crystalline specimens. For comparison, NMR investigations of non-doped and La-or Co-doped M-type Sr ferrites are also performed. Ferrimagnetic M-type Sr ferrite contains the following five crystallographic Fe sites: the majority spin sites 12k, 2a, and 2b, and the minority spin sites 4f1 and 4f2. Based on 57 Fe and 59 Co NMR, a plausible model of (La, Co)-codoped Sr ferrite is deduced. To a considerable degree, the charge compensation between La 3+ and Co 2+ works in the equal (La, Co)-codoped case, where more than half of the Co ions are considered to be present in the minority spin 4f1 sites at the center of the oxygen tetrahedra, with the S=3/2 state carrying a small orbital moment owing to spin-orbit interaction. The remaining small number of high-spin Co 2+ (S=3/2, L=1) ions with unquenched orbital moments would be distributed to the other octahedral 12k, 2a, and 4f2 sites.

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Section: Introductionmentioning

confidence: 84%

“…The NMR peak positions are consistent with those shown in previous studies for M-type Ba and Sr ferrites. 12,13,[18][19][20][21] The site assignments of the NMR peaks are denoted in Fig. 2.…”

Section: Wyckoff Notation Oxygen Coordination Moment Direction 2amentioning

confidence: 99%

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite: Fe57 and Co59 nuclear magnetic resonance studies

et al. 2018

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“…NMR measurements have revealed the presence of Fe 2+ ions on both 4 f VI and 6 g octahedral sites . Based on results of magnetic moment measurements, Mössbauer spectroscopy, 57 Fe NMR, and ab initio calculations it was demonstrated recently, that the Fe 2+ ions in SrFe 2 ‐W ferrite are located in spin‐up 6g and 4f VI octahedral sites …”

Section: Introductionmentioning

confidence: 99%

Phase stability and magnetic properties of SrFe₁₈O₂₇ W‐type hexagonal ferrite

2019

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W‐type SrFe22+Fe163+normalO27 ferrite is a member of the hexagonal ferrite family and a potential permanent magnet material. However, its synthesis conditions are not fully understood yet. Samples were sintered either at 1400°C in air and quenched, or at 1300°C at reduced oxygen partial pressure. The precise stability conditions of this W‐type ferrite were investigated in the temperature range of 1200°C‐1400°C using thermogravimetry, XRD, and electron microscopy. At 1300°C, the ferrite is stable at oxygen partial pressures of -3.1≤logpO2≤-1.6. At more oxidizing conditions, the ferrite decomposes into M‐type ferrite and hematite, while at more reducing atmospheres Sr4Fe6O13 and magnetite are formed. The nonstoichiometry δ of SrFe18−δO27 was derived from thermal analysis data at 1300°C as function of oxygen partial pressure and was found to be mainly due to cation vacancies. Magnetization measurements show that this W‐type ferrite exhibits Ms = 103 emu/g at T = 4 K, which agrees well with a ferrimagnetic spin arrangement according to Gorter's model. As alternative, Zn‐substituted W‐ferrite was found to be stable in air at 1200°C with a large Ms = 123 emu/g at 4 K.

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“…The hexagonal ferrite type-M is denoted by the formula MFe 12 O 19 , where M is a divalent metal ion, typically Sr 2+ , Ba 2+ , or Pb 2+ [2]. Since its discovery in 1950 [3], the hexagonal ferrite type-M SrFe 12 O 19 has played an important role in hard magnetic materials and has been studied for decades due to its good chemical stability, ferrimagnetic behavior, high Curie temperature, high saturation magnetization, high coercivity, high magneto-crystalline anisotropy (MCA), and it is inexpensive compared to similar compounds [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Effect of Sonication Output Power on the Crystal Structure and Magnetism of SrFe12O19 Nanoparticles

et al. 2018

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Abstract:We reported the effect of the sonication output power (SOP), from 120, 180, to 240 W, on the crystal structure, morphology, and magnetic properties of SrFe 12 O 19 nanoparticles synthesized by sonochemical process assisted with heat treatment. X-ray Diffraction analysis of the obtained powder showed the formation of Fe 3 O 4 with low crystallinity degree, which increased with the increase in SOP, together in a crystalline phase identified as SrCO 3 . The formation of SrFe 12 O 19 started at 1073 K, and was completed at 1173 K. However, hexaferrite was obtained with the secondary phases α-Fe 2 O 3 and SrFeO 2.5 . At 1323 K, the secondary phases vanished, and a single phase SrFe 12 O 19 was detected. Vibrating Sample Magnetometry analysis showed that the SrFeO 2.5 phase caused the formation of a hysteresis loop known as the Perminvar magnetic hysteresis loop. At 1323 K, the powder synthesized at 120 W showed a specific magnetization of 67.15 Am 2 /kg at 1.43 × 10 6 A/m, and coercivity of 4.69 × 10 4 A/m, with a spherical-like morphology and average particle size of 56.81 nm obtained by Scanning Electron Microscopy analysis. The increment of SOP promoted a high degree of crystallinity and decrease in crystal size. Additionally, it promoted the formation of secondary phases, induced agglomeration, and modified the morphology of the particles.

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Hexagonal ferrites of X-, W-, and M-type in the system Sr–Fe–O: A comparative study

Cited by 40 publications

References 27 publications

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite: Fe57 and Co59 nuclear magnetic resonance studies

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite: Fe57 and Co59 nuclear magnetic resonance studies

Phase stability and magnetic properties of SrFe₁₈O₂₇ W‐type hexagonal ferrite

Effect of Sonication Output Power on the Crystal Structure and Magnetism of SrFe12O19 Nanoparticles

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Hexagonal ferrites of X-, W-, and M-type in the system Sr–Fe–O: A comparative study

Cited by 40 publications

References 27 publications

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite: Fe57 and Co59 nuclear magnetic resonance studies

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite: Fe57 and Co59 nuclear magnetic resonance studies

Phase stability and magnetic properties of SrFe18O27 W‐type hexagonal ferrite

Effect of Sonication Output Power on the Crystal Structure and Magnetism of SrFe12O19 Nanoparticles

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Phase stability and magnetic properties of SrFe₁₈O₂₇ W‐type hexagonal ferrite