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

Platelets of strontium hexaferrite (SrFe12O19, 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 simulationsThis work is supported by the Spanish Ministry of Economy and Competitiveness through Projects MAT2015-64110-C2-1-P, MAT2015-64110-C2-2-P, MAT2015-66888-C3-1-R and by the European Commission through Project H2020 No. 720853 (Amphibian). These experiments were performed at the CIRCE, MISTRAL and BOREAS beamlines of the ALBA Synchrotron Light Facility. G.D.S. acknowledges the European Youth Employement Initiative and the Autonomous Community of Madrid for a one-year fellowship. Slovenian Research Agency is acknowledged for funding the research program Ceramics and complementary materials for advanced engineering and biomedical applications (P2-0087), CEMM, JSI for the use of TE

Cement-in-cement stem revision for Vancouver type B periprosthetic femoral fractures after total hip arthroplasty: A 3-year follow-up of 23 cases

Background and purpose Revision surgery for periprosthetic femoral fractures around an unstable cemented femoral stem traditionally requires removal of existing cement. We propose a new technique whereby a well-fixed cement mantle can be retained in cases with simple fractures that can be reduced anatomically when a cemented revision is planned. This technique is well established in femoral stem revision, but not in association with a fracture

Ligament contribution to patterns of articular fractures of the distal radius

PurposeIntra-articular fractures of the distal radius are common injuries, but the correlation between ligament attachments and fracture location is poorly understood. The purpose of this study was to assess the location of intra-articular fractures compared to the known ligament attachments of the distal radius.MethodsThe authors retrospectively reviewed computed tomography scans of acute intra-articular distal radius fractures performed at 1 institution between 2001 and 2008. Of 145 scans, 45 were deemed unsuitable due to poor quality or presence of internal fixation in the distal radius, leaving 100 fractures for review. Fracture line locations of the distal radius were plotted to a standardized distal radius template and statistically analyzed for their relationship to known ligament attachments.ResultsFracture lines were significantly more likely to occur at the intervals between the ligament attachments than at the ligament attachments. Common sites of fractures were the center of the sigmoid notch, between the short and long radiolunate ligaments, and the central and ulnar aspects of the scaphoid fossa dorsally. The sites of the ligament attachments to the distal radius were relatively protected. The likely site of the impaction of the carpus on the distal radius articular surface can often be construed from viewing the computed tomography scans, and the subsequent propagation of the fracture can be identified.ConclusionsArticular fractures of the distal radius are statistically more likely to occur between the ligament attachments. The ligamentous attachments of the distal radius to the volar carpus in an intra-articular distal radius fracture are relatively well preserved.Type of study/level of evidenceDiagnostic III.Daniel G. Mandziak, Adam C. Watts, Gregory I. Bai

Motion of magnetic domain walls and vortices in epitaxial magnetite microstructures

6 pags., 4 figs.We report on the response of magnetic domains in thin magnetite microstructures to weak external magnetic fields. Magnetite islands were grown by high-temperature oxygen-assisted molecular beam epitaxy on Ru(0001). The islands, micrometric wide and tens of nanometers thick are of high structural quality, each having been grown from a single nucleation center. Their magnetic domain structure is dominated by shape anisotropy, i.e., they present Landau flux-closure domain configurations. The magnetic domains of the in situ grown microstructures have been imaged directly by means of x-ray magnetic circular dichroism in photoemission electron microscopy while applying external, in-plane magnetic fields along different directions. Upon application of an external field the Landau state vortex core experiences a displacement along a direction perpendicular to the excitation field. The behavior of the Landau state under the applied magnetic field is quantified and compared with micromagnetic simulations. The results highlight the bulk-like magnetic properties of the nanometer-thick microstructures, opening the way to their possible use in technological applications.This work is supported by Projects No. RTI2018-095303-B-C51, and RTI2018-095303-B-C53 and PID2021-124585NB-C31 funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe and by the Comunidad de Madrid, Spain through Project. NANOMAGCOST-CM P2018/NMT-4321. These experiments were performed at the CIRCE beamline of the ALBA Synchrotron Light Facility. A. M. acknowledges funding via a CSIC-Alba agreementPeer reviewe

Structural and magnetic properties of transition metal oxide thin films grown on Ru(0001)

9th IWSP: Nanostructured surfaces, Trzebnica, Poland, 24 – 28 June 2019. -- http://www.iwsp2019.ifd.uni.wroc.pl/Transition metal oxides (TMO) are promising candidate materials for future spintronic devices. Their properties arise from the interaction between transition metal and oxygen ions in a given structure which are very sensitive to different bond length and angles, as well as to their particular cationic distribution. However, their properties in thin film form, as required for the use in microelectronic devices, are often disappointing, since interface and surface effects, as well as defects can play strong roles. Thus, a detailed understanding of magnetic and transport properties of ultrathin films at such scale are needed, which enables us to optimize the fabrication methods. Here we demonstrate a route for preparing high quality ultrathin ternary transition metal oxide films on a metallic substrate. Mixed nickel, iron and cobalt oxides have been grown on Ru(0001) by high temperature oxygen- assisted molecular beam epitaxy. The nucleation and growth process are observed in real time by means of Low Energy Electron Microscopy (LEEM), which enables to optimize of the growth parameters. A comprehensive characterization is performed combining LEEM and LEED for structural characterization and PEEM (PhotoEmission Electron Microscopy) with synchrotron radiation for chemical and magnetic analysis via X-ray Absorption Spectroscopy, X-ray Magnetic Circular Dichroism and X-ray Magnetic Linear Dichroism (XAS-PEEM, XMCD-PEEM and XMLD- PEEM, respectively). Depending on the chosen stoichiometry and conditions, either spinel ferrites or monoxides of rocksalt structure can be prepared. The spinel ferrites show ferromagnetic contrast. While the monoxide one present long range antiferromagnetic ordering with the Néel temperature above the room temperature. The high crystalline and morphological quality of prepared films result in optimized properties with respect to films grown by other methods, such as magnetic domains which are larger by several orders of magnitude

Magnetic domain wall pinning in cobalt ferrite microstructures

A detailed correlative structural, magnetic and chemical analysis of (non-stoichiometric) cobalt ferrite micrometric crystals was performed by x-ray magnetic circular dichroism combined with photoemission microscopy, low-energy electron microscopy and atomic force microscopy. The magnetization vector inside the islands was resolved at the nanoscale, as obtained from magnetic images taken at different x-ray incidence angles. The location of the magnetic domain walls was correlated with the presence of different types of defects as revealed by the different microscopies. This, together with the results of micromagnetic simulations, suggests that the main source of pinning in these microcrystals are linear structural defects induced in the spinel structure by the substrate steps underneath the islands. Our result is of relevance for understanding the different magnetic properties of thin films and nanostructures as compared with the corresponding bulk materials. © 2022 The Author

Understanding the magnetic behavior of a combined magnetically hard and soft layer system

CMD2020GEFES, onlin