A5009051588- Multiferroics and related materials
- Ferroelectric and Piezoelectric Materials
- Magnetic properties of thin films
- Magnetic Properties and Synthesis of Ferrites
- Magnetic and transport properties of perovskites and related materials
- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- Metallic Glasses and Amorphous Alloys
- Magnetic Properties and Applications
- Diamond and Carbon-based Materials Research
- Rare-earth and actinide compounds
- Magnetic Properties of Alloys
- Acoustic Wave Resonator Technologies
- Theoretical and Computational Physics
- Microwave Dielectric Ceramics Synthesis
- Copper-based nanomaterials and applications
- Metal and Thin Film Mechanics
- Solid-state spectroscopy and crystallography
- Magneto-Optical Properties and Applications
- Electrophoretic Deposition in Materials Science
- Copper Interconnects and Reliability
- Advanced Condensed Matter Physics
- Advanced Physical and Chemical Molecular Interactions
- Acoustic Wave Phenomena Research
- Material Dynamics and Properties
University of Minho
2006-2024
Polytechnic Institute of Porto
2009-2024
Instituto Politécnico Nacional
2014
Universidade do Porto
1993-1999
Abstract Nanocomposite thin films composed by (BaTiO 3 ) 1– x –(CoFe 2 O 4 with different cobalt ferrite concentrations ( have been deposited pulsed laser ablation on platinum covered Si(001) substrates. The structure was studied X‐ray diffraction and Raman spectroscopy. It found that the CoFe phase unit cell compressed along growth direction of films, it relaxed increasing . opposite behavior observed in BaTiO where lattice parameters obtained from measurements presented a progressive...
Detailed structural and magnetic measurements were performed on nanostructured composite thin films of cobalt ferrite (CoFe2O4-magnetostrictive) dispersed in a barium titanate (BaTiO3-piezoelectric) matrix, with different CoFe2O4 concentrations (ranging from x=20% to x=70%). The deposited by laser ablation platinum covered Si(100). Their structure was studied x-ray diffraction Raman spectroscopy. properties measured superconducting quantum inteference device magnetometer. nanocomposite...
Co 48 Ag 52 films prepared by sputtering at 77 K were characterized magnetoresistance (MR) and magnetization. MR measurements give evidence for an important positive anisotropic (AMR) in the as-deposited samples that reaches ∼11% 15 saturates H≈2 kOe. For higher applied fields is reversible well described a square Langevin function indicating giant behavior mostly due to superparamagnetic particles. The AMR becomes negligible after annealing 350 °C 10 min, probably stress relief.
The structural and magnetic properties of cobalt ferrite (CoFe2O4) thin films deposited by electrophoresis on p-doped Si(001) substrates have been characterized. were polycrystalline composed with the cubic spinnel structure. observed decrease coercive field sixth power grain size was indicative a competition between magnetocrystalline anisotropy exchange coupling energy, these randomly oriented nanosized grained films.
Chain reorientation may be induced in polyvinylidene fluoride (PVDF) its β-phase by applying a deformation perpendicular to the pre-oriented polymeric chains. This begins right after yielding point and seems completed when stress-strain curve stabilizes. We have studied chain mechanism scanning electron microscopy (SEM) dielectric relaxation methods we analyzed influence α- β-relaxations of polymer. SEM images confirm existence upon transversal deformation. The decrease crystallinity with...
Thin film nanogranular composites of cobalt ferrite (CoFe2O4) dispersed in a barium titanate (BaTiO3) matrix were deposited by laser ablation with different concentrations (x). Their structural and magnetic properties characterized. The films polycrystalline composed mixture tetragonal-BaTiO3 CoFe2O4 the cubic spinel structure. A slight (111) phase orientation (311) observed. lattice parameter was always smaller than bulk value indicating that under compressive stress. From atomic force...
Thin film nanocomposites composed by CoFe2O4 grains, deposited electrophoresis, and subsequently covered a laser ablation BaTiO3 layer, were prepared with different cobalt ferrite concentrations (x). The phase was under compressive strain that relaxed as the concentration increased. Consequently, blueshift of Raman peaks observed, decreased increasing x. dielectric permittivity films found to decrease concentration, due barium titanate layer grain size content in films.
Multiferroic bilayer thin films composed by LiNbO3 and CoFe2O4 were prepared laser ablation over (100) platinum-covered Si substrates, to understand the influence of layer thickness on their structural, electric dielectric properties. The dense polycrystalline, presenting rhombohedral cubic spinel layers. unit cell experienced compression along growth direction films, whereas exhibited a structural distortion in its cell. These strain effects due mechanical interaction between both layers...
The magnetoresistive behavior of granular thin films prepared by Fe and Co implantation in Ag is reported. (∼2000 Å) were deposited evaporation or laser ablation onto Si SiO2 substrates implanted with at fluences up to 1017 at. %/cm2. response obtained after was found increase the fluence. An a factor 3–4 can be achieved annealing conventional furnace 620 K under vacuum. best value magnetoresistance so far 9% 10 1.5% room temperature for film fluence 8×1016 %/cm2 annealed K.
Thin film nanocomposites with mixed connectivity, composed by CoFe2O4 grains, deposited electrophoresis on Si|Pt substrates, and subsequently covered a laser ablation BaTiO3 layer were prepared different cobalt ferrite concentrations. Their structure presented combination of BaTiO3, its tetragonal the orthorhombic phases coexisting at room temperature, cubic spinel structure. The nanograins under in-plane tensile stress, while phase was compressive stress. dielectric measurements showed that...
Premature degradation of ordinary Portland cement (OPC) concrete infrastructures is a current and serious problem with overwhelming costs amounting to several trillion dollars. The use surface treatments waterproofing materials prevent the access aggressive substances an important way enhancing durability. most common polymeric resins based on epoxy, silicone (siloxane), acrylics, polyurethanes or polymethacrylate. However, epoxy have low resistance ultraviolet radiation while are sensitive...
Vanadium oxides are a class of materials with outstanding physical and chemical properties. They find wide field technological applications such as optical electrical switching devices, light detectors, temperature sensors, micro batteries, etc. There several studies regarding the production vanadium oxide films by radio-frequency (RF) magnetron sputtering, increasing interest on thermochromic VO2 phase. However, literature focus deposited direct current (DC) sputtering is very limited. In...
Laser ablation was used to successfully fabricate multiferroic bilayer thin films, composed of BaTiO3 (BTO) and CoFe2O4 (CFO), on highly doped (100) Si substrates. This study investigates the influence layer thickness (50–220 nm) films’ structural, magnetic, dielectric properties. The dense, polycrystalline films exhibited a tetragonal phase cubic spinel layer. Structural analysis revealed compression unit cell along growth direction, while showed distortion, more pronounced in thinner BTO...
A method for investigating the nature of thermally activated relaxations in terms their cooperative character is tested both low molecular weight crystals and polymers. This approach based on analysis activation entropy. In betaine arsenate/phosphate (BABP) mixed systems we will study effect pressure concentration, whereas rubidium ammonium dihydrogen arsenate (RADA) crystal system concentration deuteration relaxation processes be studied. Several have been also studied polymeric systems,...