Strontium hexaferrite platelets: a comprehensive soft X-ray absorption and Mössbauer spectroscopy study

Abstract

Platelets of strontium hexaferrite (SrFe 12 O 19 , SFO), up to several micrometers in width, and tens of nanometers thick have been synthesized by a hydrothermal method. They have been studied by a combination of structural and magnetic techniques, with emphasis on Mössbauer spectroscopy and X-ray absorption based-measurements including spectroscopy and microscopy on the iron-L edges and the oxygen-K edge, allowing us to establish the differences and similarities between our synthesized nanostructures and commercial powders. The Mössbauer spectra reveal a greater contribution of iron tetrahedral sites in platelets in comparison to pure bulk material. For reference, high-resolution absorption and dichroic spectra have also been measured both from the platelets and from pure bulk material. The O-K edge has been reproduced by density functional theory calculations. Out-of-plane domains were observed with 180° domain walls less than 20 nm width, in good agreement with micromagnetic simulations.

Magnetic performance enhancement in La-Ca-Co doped SrFe12O19 ferrite permanent magnets via cold isostatic pressing

“…Permanent magnetic materials including rare-earth permanent magnets (REPMs) and ferrite permanent magnets (FPMs) are indispensable fundamental materials in modern society that play a key role in many hightech fields [1][2][3][4][5][6][7][8][9][10]. When compared to REPMs, FPMs bear much more economical fabrication cost and stronger chemical stability, leading to their wide application in motors, loudspeakers, etc Moreover, as a kind of traditional permanent magnetic materials, FPMs have been continuously investigated during past decades to improve their magnetic properties .…”

Evidence for Conical Magnetic Structure in M‐Type BaFe12O19 Hexaferrite: A Combined Single‐Crystal X‐ray Magnetic Circular Dichroism and Neutron Diffraction Study

“…The XMCD signal at the Fe L 3 -edge shows a prominent at peak at %709.5 eV which is known to be due to the Fe 3þ ion at the octahedral site. [33,34] The magnitude of the spin moment can be estimated using the well-established sum rule [30]…”

“…m θ T is related to the magnetic dipole operator and its contribution is negligible for 3d 5 Fe 3þ . [34] To calculate spin magnetic moment using sum rule, we followed the steps discussed in the study by Chen et al [30] We first obtained the summed XAS spectra (¼ σ þ þ σ À ), then removed the edge jump using a two-step-like function and finally integrated the summed XAS spectra over the L 2,3 energy range. The variations of the XMCD signal integrated over the L 2,3 energy range and sum XAS with its integration are shown in Figure 3c,d, respectively, for H ¼ 0 T. We estimated the value of P, Q, and R using these two figures and then calculated the spin moment using Equation (1).…”

“…The peak at %709.5 eV is attributed to Fe 3þ ion at the octahedral site whereas the small peak at %708.3 eV is from Fe 3þ in trigonal bipyramid environment. [34] Using the P, Q, and R values of GI geometry for H ¼ 0 T and 0.5 T, the parallel and perpendicular components of the moment were calculated. The calculated spin moments parallel to the c-axis for the zero field (H ¼ 0 T) and H ¼ 0.5 T field are found to be m spin//c ≈ 0.2009 μ B /Fe 3þ and 0.56228 μ B /Fe 3þ , respectively, whereas those perpendicular to the c-axis are m spin⊥c ≈ 0.0538 μ B /Fe 3þ and 0.15058 μ B /Fe 3þ , respectively.…”

Σύνθετα Νανοδιηλεκτρικά Πολυμερικής Μήτρας Μαγνητικών Εγκλεισμάτων

“…SrFe12O19 είναι ο φερρίτης στον οποίο το βάριο του BaFe12O19 έχει αντικατασταθεί από μικρότερα άτομα στροντίου με πυκνότητα 5.101 g/cm 3 και μοριακή μάζα 1062 g b . Ανακαλύφθηκε και αυτός στα εργαστήρια της Philips την δεκαετία του '60 [59]. Στις περισσότερες φυσικές του ιδιότητες το SrFe12O19 μοιάζει με το BaFe12O19 [60], ωστόσο παρουσιάζει υψηλότερη μαγνήτιση και σταθερά μαγνητοκρυσταλλικής ανισοτροπίας (ΚU = 3.6 10 5 Jm -3 ) καθώς και ελαφρώς μεγαλύτερη θερμοκρασία Curie (ΤC = 732 K) [59].…”