Abstract.We study the influence of the porosity on the domain structure of cobalt antidots thin films with controlled and circular defects of 20, 40 and 60 nm of diameter. Micromagnetic simulations, combined with First-order reversal curves analysis of classical magnetometry measurements, have been used to track the evolution of the magnetic domain configurations. The found coercivity enhancement with the increase of the pore diameter is correlated to the domain reversibility. Moreover, we found that when the pores diameter increases the domain-domain interactions become dominant.
In this communication, it was evaluated the production of fatty acid ethyl ester (FAAE) from the free fatty acids of babassu oil catalyzed by lipase from Rhizomucor miehei (RML) immobilized on magnetic nanoparticles (MNP) coated with 3-aminopropyltriethoxysilane (APTES), Fe 3 O 4 @APTES-RML or RML-MNP for short. MNPs were prepared by co-precipitation coated with 3-aminopropyltriethoxysilane and used as a support to immobilize RML (immobilization yield: 94.7 ± 1.0%; biocatalyst activity: 341.3 ± 1.2 U p−NPB /g), which were also activated with glutaraldehyde and then used to immobilize RML (immobilization yield: 91.9 ± 0.2%; biocatalyst activity: 199.6 ± 3.5 U p−NPB /g). RML-MNP was characterized by X-Ray Powder Diffraction (XRPD), Fourier Transform-Infrared (FTIR) spectroscopy and Scanning Electron Microscope (SEM), proving the incorporation and immobilization of RML on the APTES matrix. In addition, the immobilized biocatalyst presented at 60 • C a half-life 16-19 times greater than that of the soluble lipase in the pH range 5-10. RML and RML-MNP showed higher activity at pH 7; the immobilized enzyme was more active than the free enzyme in the pH range (5-10) analyzed. For the production of fatty acid ethyl ester, under optimal conditions [40 • C, 6 h, 1:1 (FFAs/alcohol)] determined by the Taguchi method, it was possible to obtain conversion of 81.7 ± 0.7% using 5% of RML-MNP.
In this work, multilayers of Co/Pd with out of plane anisotropy have been deposited on the bottom of porous alumina membranes, forming nanodomes films with 100 and 200 nm diameter. The magnetization reversal of the multilayers is investigated by magnetization curves, extraordinary Hall effect and magnetic force microscopy (MFM) experiments. The results show that as the pore diameter increase, a larger hall resistivity is obtained, compared with the continuous film.
With the continuing interest in new magnetic materials for sensor devices and data storage applications, the community needs reliable and sensitive tools for the characterization of such materials. Soft X-rays tuned to elemental absorption edges are a depth and element sensitive probe of magnetic structure at the nanoscale, and scattering measurements have the potential to provide 3D magnetic structural information of the material. In this work we develop a methodology in transmission geometry that allows one to probe the spatial distribution of the magnetization along the different layers of magnetic heterostructures. We study the in-plane/out-of-plane transition of magnetic domains in multilayer thin film systems consisting of two layers of NiFe top and bottom, and a 50 repeat Co/Pd multilayer in the centre. The experimental data are analysed by simulating scattering data starting from micromagnetic simulations, and we find that the out of plane domains of the Co/Pd multilayer intrude into the NiFe layers to a greater extent than would be expected from micromagnetic simulations performed using the standard magnetically isotropic input parameters for the NiFe layers.
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