3 research outputs found
Interfacial Dzyaloshinskii-Moriya interaction in epitaxial W/Co/Pt multilayers
Dzyaloshinskii-Moriya interaction (DMI) manifesting in asymmetric layered
ferromagnetic films gives rise to non-colinear spin structures stabilizing
magnetization configurations with nontrivial topology. In this work
magnetization reversal, domain structure, and strength of DMI are related with
the structure of W/Co/Pt multilayers grown by molecular beam epitaxy. Applied
growth method enables fabrication of layered systems with higher crystalline
quality than commonly applied sputtering techniques. As a result, a high value
of D coefficient was determined from the aligned magnetic domain stripe
structure, substantially exceeding 2 mJ/m2. The highest value of DMI value
D = 2.64mj/m2 and strength of surface DMI parameter DS = 1.83pJ/m for
N=10 has been observed. Experimental results coincide precisely with those
obtained from structure based micromagnetic modelling and density functional
theory calculations performed for well-defined layered stacks. This high value
of DMI strength originates from dominating contributions of the interfacial
atomic Co layers and additive character from both interface types
A comprehensive study of pristine and calcined f-MWCNTs functionalized by nitrogen-containing functional groups
We present the study of pristine and calcined f-MWCNTs functionalized by nitrogen-containing
functional groups. We focus on the structural and microstructural modification tuned by
the previous annealing. However, our primary goal was to analyze the electronic structure and
magnetic properties in relation to the structural properties using a multi-technique approach. The
studies carried out by X-ray diffraction, XPS, and 57Fe Mössbauer spectrometry revealed the presence
of -Fe nanoparticles, Fe3C, and -FeOOH as catalyst residues. XPS analysis based on the deconvolution
of core level lines confirmed the presence of various nitrogen-based functional groups
due to the purification and functionalization process of the nanotubes. The annealing procedure
leads to a structural modification mainly associated with removing surface impurities as purification
residues. Magnetic studies confirmed a significant contribution of Fe3C as evidenced by a Curie
temperature estimated at TC = 452 15K. A slight change in magnetic properties upon annealing
was revealed. The detailed studies performed on nanotubes are extremely important for the further
synthesis of composite materials based on f-MWCNTs
Evolution of Structural and Magnetic Properties of Fe-Co Wire-like Nanochains Caused by Annealing Atmosphere
Thermal treatment is a post-synthesis treatment that aims to improve the crystallinity and interrelated physical properties of as-prepared materials. This process may also cause some unwanted changes in materials like their oxidation or contamination. In this work, we present the post-synthesis annealing treatments of the amorphous Fe1−xCox (x = 0.25; 0.50; 0.75) Wire-like nanochains performed at 400 °C in two different atmospheres, i.e., a mixture of 80% nitrogen and 20% hydrogen and argon. These processes caused significantly different changes of structural and magnetic properties of the initially-formed Fe-Co nanostructures. All of them crystallized and their cores were composed of body-centered cubic Fe-Co phase, whereas their oxide shells comprised of a mixture of CoFe2O4 and Fe3O4 phases. However, the annealing carried out in hydrogen-containing atmosphere caused a decomposition of the initial oxide shell layer, whereas a similar process in argon led to its slight thickening. Moreover, it was found that the cores of thermally-treated Fe0.25Co0.75 nanochains contained the hexagonal closest packed (hcp) Co phase and were covered by the nanosheet-like shell layer in the case of annealing performed in argon. Considering the evolution of magnetic properties induced by structural changes, it was observed that the coercivities of annealed Fe-Co nanochains increased in comparison with their non-annealed counterparts. The saturation magnetization (MS) of the Fe0.25Co0.75 nanomaterial annealed in both atmospheres was higher than that for the non-annealed sample. In turn, the MS of the Fe0.75Co0.25 and Fe0.50Co0.50 nanochains annealed in argon were lower than those recorded for non-annealed samples due to their partial oxidation during thermal processing