| 1. |
- Bonanni, Valentina, et al.
(författare)
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First order reversal curve analysis of graded anisotropy FePtCu films
- 2010
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 97:20
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Tidskriftsartikel (refereegranskat)abstract
- The reversal mechanisms of graded anisotropy FePtCu films have been investigated by alternating gradient magnetometer (AGM) and magneto-optical Kerr effect (MOKE) measurements with first-order reversal curve (FORC) techniques. The AGM-FORC analysis, which clearly shows the presence of soft and hard components, is unable to resolve how these phases are distributed throughout the film thickness. MOKE-FORC measurements, which preferentially probe the surface of the film, reveal that the soft components are indeed located toward the top surface. Combining AGM-FORC with the inherent surface sensitivity of MOKE-FORC analysis allows for a comprehensive analysis of heterogeneous systems such as graded materials.
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| 2. |
- Bousquet, Jean, et al.
(författare)
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Allergic Rhinitis and its Impact on Asthma (ARIA) Phase 4 (2018) : Change management in allergic rhinitis and asthma multimorbidity using mobile technology
- 2019
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Ingår i: Journal of Allergy and Clinical Immunology. - : Elsevier. - 0091-6749 .- 1097-6825. ; 143:3, s. 864-879
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Tidskriftsartikel (refereegranskat)abstract
- Allergic Rhinitis and its Impact on Asthma (ARIA) has evolved from a guideline by using the best approach to integrated care pathways using mobile technology in patients with allergic rhinitis (AR) and asthma multimorbidity. The proposed next phase of ARIA is change management, with the aim of providing an active and healthy life to patients with rhinitis and to those with asthma multimorbidity across the lifecycle irrespective of their sex or socioeconomic status to reduce health and social inequities incurred by the disease. ARIA has followed the 8-step model of Kotter to assess and implement the effect of rhinitis on asthma multimorbidity and to propose multimorbid guidelines. A second change management strategy is proposed by ARIA Phase 4 to increase self-medication and shared decision making in rhinitis and asthma multimorbidity. An innovation of ARIA has been the development and validation of information technology evidence-based tools (Mobile Airways Sentinel Network [MASK]) that can inform patient decisions on the basis of a self-care plan proposed by the health care professional.
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| 3. |
- Chen, Jianing, et al.
(författare)
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Plasmonic Nickel Nanoantennas
- 2011
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Ingår i: SMALL. - : Wiley. - 1613-6810 .- 1613-6829. ; 7:16, s. 2341-2347
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Tidskriftsartikel (refereegranskat)abstract
- The fundamental optical properties of pure nickel nanostructures are studied by far-field extinction spectroscopy and optical near-field microscopy, providing direct experimental evidence of the existence of particle plasmon resonances predicted by theory. Experimental and calculated near-field maps allow for unambiguous identification of dipolar plasmon modes. By comparing calculated near-field and far-field spectra, dramatic shifts are found between the near-field and far-field plasmon resonances, which are much stronger than in gold nanoantennas. Based on a simple damped harmonic oscillator model to describe plasmonic resonances, it is possible to explain these shifts as due to plasmon damping.
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| 4. |
- Dahlberg, D, et al.
(författare)
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Measurements of the ferromagnetic/antiferromagnetic interfacial exchange energy in CO/CoO and Fe/FeF2 layers
- 1998
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 83:11, s. 6893-6895
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Tidskriftsartikel (refereegranskat)abstract
- Two measurement techniques, both relying on reversible rotations of the magnetization, have been used to determine the magnitude of the interfacial exchange energy (IEE) between ferromagnetic and antiferromagnetic (F/AF) layers. One technique is to use the anisotropic magnetoresistance to determine rotations of the magnetization away from the unidirectional easy axis, where the rotation is accomplished by applying external magnetic fields less than the effective F/AF exchange field. The second technique uses measurements of the ac susceptibility as a function of the angle between the ac field and the unidirectional exchange field. Both of the reversible process techniques result in values of the IEE larger (by as much as a factor of 10 in Co/CoO bilayers) than the traditional irreversible technique of measuring a shift in the hysteresis loop. The ac susceptibility technique was also used to measure one Fe/FeF2 bilayer. For this sample, the IEE values obtained by reversible and irreversible methods are equivalent.
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| 5. |
- De Toro, José A., et al.
(författare)
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Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles
- 2017
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Ingår i: Chemistry of Materials. - Washington, D.C., USA : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 29:19, s. 8258-8268
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Tidskriftsartikel (refereegranskat)abstract
- Remanence magnetization plots (e.g., Henkel or delta M plots) have been extensively used as a straightforward way to determine the presence and intensity of dipolar and exchange interactions in assemblies of magnetic nanoparticles or single domain grains. Their evaluation is particularly important in functional materials whose performance is strongly affected by the intensity of interparticle interactions, such as patterned recording media and nanostructured permanent magnets, as well as in applications such as hyperthermia and magnetic resonance imaging. Here, we demonstrate that delta M plots may be misleading when the nanoparticles do not have a homogeneous internal magnetic configuration. Substantial dips in the delta M plots of gamma-Fe2O3 nanoparticles isolated by thick SiO2 shells indicate the presence of demagnetizing interactions, usually identified as dipolar interactions. results, however, demonstrate that it is the inhomogeneous spin structure of the nanoparticles, as most clearly evidenced by Mossbauer measurements, that has a pronounced effect on the delta M plots, leading to features remarkably similar to those produced by dipolar interactions. X-ray diffraction results combined with magnetic characterization indicate that this inhomogeneity is due to the presence of surface structural (and spin) disorder. Monte Carlo simulations unambiguously corroborate the critical role of the internal magnetic structure in the delta M plots. Our findings constitute a cautionary tale on the widespread use of remanence plots to assess interparticle interactions as well as offer new perspectives in the use of Henkel and delta M plots to quantify the rather elusive inhomogeneous magnetization states in nanoparticles.
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| 6. |
- Dumas, Randy K., et al.
(författare)
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Graded Anisotropy FePtCu Films
- 2011
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 47:6, s. 1580-1586
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Tidskriftsartikel (refereegranskat)abstract
- The fabrication and subsequent analysis of continuously graded anisotropy films are discussed. During deposition, a compositional gradient is first achieved by varying the Cu concentration from Cu-rich (Fe53Pt47)(70)Cu-30 to Cu-free Fe53Pt47. The anisotropy gradient is then realized after thermal post-annealing, and by utilizing the strong composition dependence of the low-anisotropy (A1) to high-anisotropy (L1(0)) ordering temperature. The magnetic properties are investigated by surface sensitive magneto-optical Kerr effect and alternating gradient magnetometer (AGM) measurements. AGM first-order reversal curve (FORC) measurements are employed in order to provide a detailed analysis of the reversal mechanisms, and therefore the induced anisotropy gradient. At low annealing temperatures, the FORC measurements clearly indicate the highly coupled reversal of soft and hard phases. However, significant interdiffusion results in virtually uniform films at elevated annealing temperatures. Additionally, the A1 to L1(0) ordering process is found to depend on the film thickness.
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| 7. |
- Dumas, Randy K., et al.
(författare)
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Probing vertically graded anisotropy in FePtCu films
- 2011
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Ingår i: Physical Review B. - 1098-0121 .- 1550-235X. ; 84, s. 054434-
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Tidskriftsartikel (refereegranskat)abstract
- Field-dependent polarized neutron reflectivity (PNR) and magnetometry are employed to study the magnetic properties of compositionally uniform and graded FePtCu films as a function of annealing temperature (TA). The PNR results are able to directly probe the compositional and anisotropy variations through the film thickness. Further details about how the reversal mechanisms evolve are then elucidated by using a first-order reversal curve technique. The reversal of the graded sample annealed at 300°C occurs by an initial rapid switching of the dominant soft A1 phase toward the surface of the film, followed by the gradual reversal of the residual hard phase components toward the bottom. This indicates that the anisotropy gradient is not well established at this low TA. A fundamentally different mechanism is found after annealing at 400°C, where the rapid switching of the entire film is preceded by a gradual reversal of the soft layers. This suggests that the anisotropy gradient has become better established through the film thickness. The field-dependent PNR measurements confirm the existence of an anisotropy gradient, where the lower (higher) anisotropy portions are now toward the bottom (top) of the film because of the Cu compositional gradient. However, after annealing at 500°C, a single rapid reversal is found, indicating the formation of a uniform hard film. In this case, PNR demonstrates a more uniform magnetic depth profile that is consistent with a uniform reference sample, suggesting significant interdiffusion of the Cu is degrading the compositional and induced anisotropy gradient at this elevated TA.
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| 8. |
- Estrader, Marta, et al.
(författare)
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Origin of the large dispersion of magnetic properties in nanostructured oxides : FexO/Fe3O4 nanoparticles as a case study
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 7:7, s. 3002-3015
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Tidskriftsartikel (refereegranskat)abstract
- The intimate relationship between stoichiometry and physicochemical properties in transition-metal oxides makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between the magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxides.
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| 9. |
- Fornara, Andrea, 1980-
(författare)
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Magnetic nanostructured materials for advanced bio-applications
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the recent years, nanostructured magnetic materials and their use in biomedical and biotechnological applications have received a lot of attention. In this thesis, we developed tailored magnetic nanoparticles for advanced bio-applications, such as direct detection of antibodies in biological samples and stimuli responsive drug delivery system. For sensitive and selective detection of biomolecules, thermally blocked iron oxide nanoparticles with specific magnetic properties are synthesized by thermal hydrolysis to achieve a narrow size distribution just above the superparamagnetic limit. The prepared nanoparticles were characterized and functionalized with biomolecules for use in a successful biosensor system. We have demonstrated the applicability of this type of nanoparticles for the detection of Brucella antibodies as model compound in serum samples and very low detection limits were achieved (0.05 mg/mL). The second part is concerning an in-depth investigation of the evolution of the thermally blocked magnetic nanoparticles. In this study, the formation of the nanoparticles at different stages during the synthesis was investigated by high resolution electron microscopy and correlated to their magnetic properties. At early stage of the high temperature synthesis, small nuclei of 3.5 nm are formed and the particles size increases successively until they reach a size of 17-20 nm. The small particles first exhibit superparamagnetic behavior at the early stage of synthesis and then transform to thermally blocked behavior as their size increases and passes the superparamagnetic limit. The last section of the Thesis is related to the development of novel drug delivery system based on magnetically controlled release rate. The system consists of hydrogel of Pluronic FP127 incorporating superparamagnetic iron oxide nanoparticles to form a ferrogel. The sol to gel formation of the hydrogel could be tailored to be solid at body temperature and thus have the ability to be injected inside living biological tissues. In order to evaluate the drug loading and release, the hydrophobic drug indomethacin was selected as a model compound. The drug could be loaded in the ferrogel owning to the oil in water micellar structure. We have studied the release rate from the ferrogel in the absence and presence of magnetic field. We have demonstrated that the drug release rate can be significantly enhanced by use of external magnetic field decreasing the half time of the release to more than 50% (from 3200 to 1500 min) upon the application of the external magnetic field. This makes the developed ferrogel a very promising drug delivery system that does not require surgical implant procedure for medical treatment and gives the possibility of enhancing the rate of release by external magnetic field.
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| 10. |
- Guell-Grau, Pau, et al.
(författare)
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Elastic Plasmonic-Enhanced Fabry-Perot Cavities with Ultrasensitive Stretching Tunability
- 2022
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 34:7
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Tidskriftsartikel (refereegranskat)abstract
- The emerging stretchable photonics field faces challenges, like the robust integration of optical elements into elastic matrices or the generation of large optomechanical effects. Here, the first stretchable plasmonic-enhanced and wrinkled Fabry-Perot (FP) cavities are demonstrated, which are composed of self-embedded arrays of Au nanostructures at controlled depths into elastomer films. The novel self-embedding process is triggered by the Au nanostructures catalytic activity, which locally increases the polymer curing rate, thereby inducing a mechanical stress that simultaneously pulls the Au nanostructures into the polymer and forms a wrinkled skin layer. This geometry yields unprecedented optomechanical effects produced by the coupling of the broad plasmonic modes of the Au nanostructures and the FP modes, which are modulated by the wrinkled optical cavity. As a result, film stretching induces drastic changes in both the spectral position and intensity of the plasmonic-enhanced FP resonances due to the simultaneous cavity thickness reduction and cavity wrinkle flattening, thus increasing the cavity finesse. These optomechanical effects are exploited to demonstrate new strain-sensing approaches, achieving a strain detection limit of 0.006%, i.e., 16-fold lower than current optical strain-detection schemes.
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