RESUMO
In this work, we focus on a detailed study of the role of each component layer in the multilayer structure of a magnetic tunnel junction (MTJ) as well as the analysis of the effects that the deposition parameters of the thin films have on the performance of the structure. Various techniques including atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the effects of deposition parameters on the surface roughness and thickness of individual layers within the MTJ structure. Furthermore, this study investigates the influence of thin films thickness on the magnetoresistive properties of the MTJ structure, focusing on the free ferromagnetic layer and the barrier layer (MgO). Through systematic analysis and optimization of the deposition parameters, this study demonstrates a significant improvement in the tunnel magnetoresistance (TMR) of the MTJ structure of 10% on average, highlighting the importance of precise control over thin films properties for enhancing device performance.
RESUMO
In this study, we report the influence of the Pt concentration in CoxPt100-x alloys on the catalytic activity of the alloys for 4-nitrophenol (4-NP) reduction. More precisely, a series of CoxPt100-x alloys with a Pt concentration ranging between 60% and 95% were prepared using electrodeposition at controlled potentials from stable hexachloroplatinate aqueous solution. The Pt concentration was tuned by varying the electrodeposition potential from -0.6 to -0.9 V. The changes in the CoxPt100-x alloy microstructure and crystalline structure have been investigated using SEM and TEM analysis. Our results show that the microstructure and the crystalline structure of the as-prepared materials do not depend on the electrodeposition potential. However, the catalytic activity of CoxPt100-x alloys is closely correlated with the potential applied during electrochemical synthesis, hence the Pt content. We demonstrated that the synthesized materials present a high catalytic activity (approx. 90%) after six cycles of reusability despite the fact that the Pt content of the as-prepared alloys decreases. The easy preparation method that guarantees more than 97% catalytic activity of the CoxPt100-x alloys, the easy recovery from solution, and the possibility of reusing the CoxPt100-x alloys are the benefits of the present study.
RESUMO
CoPt alloys with Pt contents from 15 to 90% were prepared using low-cost electrochemical deposition. Different samples were synthesized from electrochemical baths at pH = 2.5 and 5.5 in a solution with and without saccharin as an additive. The morphology, composition and crystalline structure of the as-prepared samples were investigated by High Resolution-Scanning Electron Microscopy (HR-SEM), Atomic Force Microscopy (AFM), Ultra-high Resolution-Transmission Electron Microscopy (UHR-TEM), Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD). XRD investigations revealed that fcc crystalline structure transforms into hcp crystalline structure when the pH of the electrochemical bath is increased from 2.5 to 5.5 as well as when saccharin is added to the electrochemical bath. The catalytic performance of the CoPt alloys for the nitro to amino phenol compounds conversion was investigated for all the prepared samples, and the results show that the conversion degree increases (from 11.4 to 96.5%) even though the Pt content in the samples decreases. From the samples prepared from the electrochemical bath with saccharin, a study regarding the effect of contact time was performed. The results indicated that after only 5 min, the CoPt sample prepared at pH = 5.5 in the presence of saccharin completely converted the nitro compound to an amino compound.
RESUMO
"Advanced Materials for Water Remediation" is a Special Issue of Materials, which will take into consideration all the papers discussing the synthesis, characterization and application of advanced materials for water remediation [...].
