Magnetic properties of epsilon iron(III) oxide nanorod arrays functionalized with gold and copper(II) oxide

A sequential chemical vapor deposition (CVD) - radio frequency (RF)-sputtering approach was adopted to fabricate supported nanocomposites based on the scarcely investigated \u3b5-iron(III) oxide polymorph. In particular, \u3b5-Fe2O3 nanorod arrays were obtained by CVD, and their subsequent functionalization with Au and CuO nanoparticles (NPs) was carried out by RF-sputtering under mild operational conditions. Apart from a multi-technique characterization of material structure, morphology and chemical composition, particular efforts were dedicated to the investigation of their magnetic properties. The pertaining experimental data, discussed in relation to the system chemico-physical characteristics, are directly dependent on the actual chemical composition, as well as on the spatial distribution of Au and CuO nanoparticles. The approach adopted herein can be further implemented to control and tailor different morphologies and phase compositions of iron oxide-based nanomaterials, meeting thus the open requests of a variety of technological utilizations

Interfirm Network Analysis in Marginal Tourist Destinations: The Mediator Company in Business Relationships

The literature on tourist destinations and the use of empirical approaches evidence the need to adopt this model to increase tourism economies. In model application, the enterprises, and local stakeholders, sometimes represent limitations or opportunities. This article opens the view to tourist destination networks, described as relational structures that can influence and determine the destination-building process. The Network Analysis methodology offers a better understanding of inter-firm relational dynamics when applied in a small context, and in this case, the application was undertaken on the island of Sicily, in Menfi town and its hinterland. Findings show the presence of a company that assumes a central role in the network, maintaining a solid web of relationships between others. In this way, a mediator company is essential in remote tourist destinations. Policymakers need to facilitate the development of tourism companies, thereby increasing the relationality and business network ties among them

Exploring the magnetic properties and magnetic coupling in SrFe12O19/Co1-xZnxFe2O4 nanocomposites

Abstract Among hard/soft nanocomposites (NCs), ferrite-based materials are potentially promising for developing exchange-coupled systems, thus leading to enhanced magnetic properties. In this regard, we investigate the role of the synthesis approach in the development of SrFe12O19/CoFe2O4 (SFO/CFO) NCs, with special focus on tuning the magnetic features of the softer phase (CFO) by introducing Zn2+ in the spinel structure. X-ray powder diffraction (XRPD), transmission electron microscopy (TEM) and squid magnetometry were employed to clarify the relationship between morphology, size, and magnetic properties of the NCs, pointing out the feasibility of this method in obtaining successfully exchange-coupled systems. This work shows how optimizing the intrinsic magnetic properties of the CFO may be used to tune the extrinsic ones of the NCs. Despite the promising results in magnetic coupling, our study clearly confirms/strengthens that an enhancement of remanent magnetization is the most important factor for improving the magnetic performance

Time and temperature dependent magnetic viscosity experiments on Sr/Co nanoferrite particles

Magnetic viscosity experiments have been performed in order to investigate the magnetization reversal in Sr nanoferrite particles (nanoscale SrFe12O19) and interacting Sr/Co nanoferrite particles (SrFe12O19-CoFe2O4 nanocomposites). The magnetic viscosity S = dM(t)/dln(t), where M(t) is the magnetization as a function of time, has been collected. For Sr nanoferrite S shows a maximum close to the coercive field, reflecting the relation between S and the energy barrier distribution. We evidence that magnetic viscosity experiments on Sr nanoferrite and interacting Sr/Co nanoferrite particles provide reliable qualitative results for the different magnetic field sweep rate and saturating field Hsat considered. In addition, the activation volumes extracted from the magnetic viscosity experiments performed at different temperatures on Sr nanoferrite are quantitatively correlated to anisotropy changes

Complex correlations between microstructure and magnetic behavior in SrFe12O19 hexaferrite nanoparticles

The magnetic properties of SrFe12O19 (SFO) hard hexaferrites are governed by the complex relation to its microstructure, determining their relevance for permanent magnets ' applications. A set of SFO nanoparticles obtained by sol-gel self-combustion synthesis was selected for an in-depth structural X-Rays powder diffraction (XRPD) characterization by means of G(L) line-profile analysis. The obtained crystallites ' size distribution reveal a clear dependence of the size along the [001] direction on the synthesis approach, resulting in the formation of platelet-like crystallites. In addition, the size of the SFO nanoparticles was determined by transmission electron microscopy (TEM) analysis and the average number of crystallites within a particle was estimated. These results have been evaluated to illustrate the formation of single-domain state below a critical value, and the activation volume was derived from time dependent magnetization measurements, aiming to clarify the reversal magnetization process of hard magnetic materials

CoCrPt@(TiO2,CoO) granular thin films grown on Ru/NixPd100-x/NiTa (x=20, 50, 80)

Structural, morphological and magnetic properties of CoCrPt@(TiO2,CoO) granular thin films deposited on Ru/NixPd100-x/NiTa intermediate layers were investigated as a function of the NixPd100-x composition (x = 20, 50, 80). Using a Ni20Pd80 buffer-layer leads to a significant improvement of the crystallographic texture, grain separation and easy-axis angular distribution with respect to conventional systems using Ru/NiTa as intermediate layers. As a result, a meaningful enhancement of magnetic properties (anisotropy constant, K = 4.1 × 105 J/m3, out-of-plane coercivity, Hc⊥ = 470 kA/m, nucleation field, HN = −115 kA/m) with respect to conventional systems (K = 3.7 × 105 J/m3, Hc⊥ = 374 kA/m, HN = −71.6 kA/m) was achieved, thus indicating that Ni20Pd80 can potentially be used as buffer-layer to enhance the recording density of conventional Hard Disk Drives

Obsidian as a Raw Material for Eco-Friendly Synthesis of Magnetic Zeolites

A sample of rhyolitic obsidian (OS) was used as raw material for zeolite synthesis by long (4 days) and fast (2 h)-aging hydrothermal processes. Zeolite synthesis was also performed by a fast (2 h) sonication method. The products were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) both immediately after and 3 years after their formation in order to determine the stability of synthetic materials according to the method used. The results confirm zeolitization of obsidian both by long-aging conventional hydrothermal heating and fast hydrothermal process. However, the data highlight the efficiency of direct ultrasound energy in achieving more stable zeolite crystals over time. These results carried out using a natural source, follow those already obtained using wastes and pure sources as raw materials thus providing a definitive validation of the different mechanisms controlling zeolite formation according to the process used. Moreover, the results confirm the effectiveness of ultrasonic energy in the formation of zeolites that are more stable over time. Due to the chemical composition of the obsidian precursor, all synthetic zeolites show good magnetic properties (i.e., saturation magnetization), in view to potential magnetic separation

Highly Controlled Dip-Coating Deposition of <i>fct</i> FePt Nanoparticles from Layered Salt Precursor into Nanostructured Thin Films: An Easy Way To Tune Magnetic and Optical Properties

Nanostructured titania films containing hard magnetic FePt nanoparticles were obtained through impregnation and postannealing of salt layered precursor [Fe­(H₂O)₆]­[PtCl₆] nanocrystals. The impregnation was performed by a highly controlled dip-coating process into ethanol based solutions of the salt precursor. The bimetallic salt nanocrystals were formed upon evaporation of the solvent into the cavities of TiO₂ template films. The salt was transformed into the hard magnetic <i>fct</i> phase by annealing in reductive atmosphere at 400 °C a particularly low conversion temperature compared with those reported for other synthesis approaches. Two different titania templates were considered. In the first case, the impregnation of 3D mesoporous films was investigated in order to determine the influence of the deposition parameters on the amount of FePt nanoparticles embedded and the final optical and magnetic properties of the layers. In the second case, this approach was further extended to 2D heterogeneous nanoperforated films. The nanoparticles were selectively deposited into the perforations thanks to a prior functionalization of the titania template by the formation of hydrophobic/hydrophilic distinct domains. Interestingly, the coalescence between the magnetic particles was found to be limited due to the low conversion temperature. This procedure of positioning particles onto a 2D nanostructured support constitutes an easy and versatile bottom-up approach toward magnetic arrays with potential application in magnetic data storage devices