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Papers by sara laureti

2018 IEEE 8th International Conference Nanomaterials: Application & Properties (NAP)

Investigating magnetic properties of nanoparticles dispersed in a fluid is catching an increasing... more Investigating magnetic properties of nanoparticles dispersed in a fluid is catching an increasing attention for their wide range of applications; however, a careful magnetic characterization requires low temperatures and vacuum conditions which represent a critical issue for a correct sample handling. In this paper, several experimental protocols to investigate low temperature magnetic properties of magnetic nanoparticles dispersed in fluid are described. In particular, by investigating interparticle interaction by remanence techniques at low temperature, some insight about particle aggregation in fluids has been given.

Advanced Functional Materials, 2021

Nanomaterials, 2021

The design of novel multifunctional materials based on nanoparticles requires tuning of their mag... more The design of novel multifunctional materials based on nanoparticles requires tuning of their magnetic properties, which are strongly dependent on the surface structure. The organic coating represents a unique tool to significantly modify the surface structure trough the bonds between the ligands of the organic molecule and the surface metal atoms. This work presents a critical overview of the effects of the organic coating on the magnetic properties of nanoparticles trough a selection of papers focused on different approaches to control the surface structure and the morphology of nanoparticles’ assemblies.

Transition metals of the 4d and 5d series close to satisfy the Stoner criterion for ferromagnetis... more Transition metals of the 4d and 5d series close to satisfy the Stoner criterion for ferromagnetism [1] can acquire a permanent magnetic moment when they are interfaced with a ferromagnet [2,3,4]. This proximity-induced magnetism rapidly decays away from the ferromagnet/non-magnetic metal (FM/NM) interface and extends for few monolayers [4,5] but has a significant influence on many properties of these systems. Magnetic proximity effect (MPE) is often linked to a strong perpendicular magnetic anisotropy, as is the case in Co/Pt and Co/Pd bilayers and multilayers, attracting considerable interest for possible applications in various fields, including information storage, sensing and biomedicine [6-9]. Relations between MPE and the Dzyaloshinskii-Moriya interaction are strongly debated [10-12] and possible consequences in the development of more efficient spintronic devices were investigated [13] Refined information on the distribution in depth of the induced magnetic moment have been o...

Magnetochemistry

Bi-magnetic core/shell nanoparticles were synthesized by a two-step high-temperature decompositio... more Bi-magnetic core/shell nanoparticles were synthesized by a two-step high-temperature decomposition method of metal acetylacetonate salts. Transmission electron microscopy confirmed the formation of an ultrathin shell (~0.6 nm) of NiO and NiFe2O4 around the magnetically hard 8 nm CoFe2O4 core nanoparticle. Magnetization measurements showed an increase in the coercivity of the single-phase CoFe2O4 seed nanoparticles from ~1.2 T to ~1.5 T and to ~2.0 T for CoFe2O4/NiFe2O4 and CoFe2O4/NiO, respectively. The NiFe2O4 shell also increases the magnetic volume of particles and the dipolar interparticle interactions. In contrast, the NiO shell prevents such interactions and keeps the magnetic volume almost unchanged.

Advanced Functional Materials

Journal of Nanoscience and Nanotechnology

Nanoscale

Thin film stacks consisting of multiple repeats of synthetic antiferromagnetic (SAF) [Co/Pd]N/Ru/... more Thin film stacks consisting of multiple repeats of synthetic antiferromagnetic (SAF) [Co/Pd]N/Ru/[Co/Pd]N units with perpendicular magnetic anisotropy were exploited as potential starting materials to fabricate free-standing micro/nanodisks, which represent a...

Nanotechnology, Jan 30, 2017

Manganese oxide nanoparticles (MNOPs), when dispersed in a water solution, show a magnetic behavi... more Manganese oxide nanoparticles (MNOPs), when dispersed in a water solution, show a magnetic behavior that drastically changes after an aging process. In this paper, the variation in the magnetic properties has been correlated with the structural evolution of the nanoparticles: in particular, the as prepared Mn3O4/MnO core/shell system manifests a low temperature magnetization reversal that is strongly affected by the presence of the MnO shell and, in particular, by the existence of a frustrated interfacial region playing a key role in determining the low temperature irreversibility, the finite coercivity slightly above the Curie temperature of the Mn3O4 phase and the horizontal displacement of the FC-hysteresis loop. On the other hand, the magnetic behavior of the aged system results dominated by the presence of Mn3O4 whose highly anisotropic character (i.e. high coercivity and high magnetization remanence) is attributed to the presence of a large fraction of surface spins. Such resu...

Journal of Physics D: Applied Physics

The effect of the deposition temperature on the crystallographic orientation of pulsed laser depo... more The effect of the deposition temperature on the crystallographic orientation of pulsed laser deposited FeCo/MgO(100) thin films is determined by means of X-Ray Reflectivity and High Resolution Trasmission Electron Microscopy analysis and correlated with the magnetic anisotropy properties measured by angle dependent hysteresis loops. All the films showed a granular structure with a high degree of crystallographic order even at very low deposition temperature (25 °C). The cubic symmetry is reflected in the angular dependence of remanent magnetization, showing a four-fold character, whose in-plane distribution is consistent with the different crystallographic orientation of the films.

Journal of biomedical materials research. Part B, Applied biomaterials, Jan 30, 2014

Aims: The aim of this work was to deposit silicon-substituted hydroxyapatite (Si-HAp) coatings on... more Aims: The aim of this work was to deposit silicon-substituted hydroxyapatite (Si-HAp) coatings on titanium for biomedical applications, since it is known that Si-HAp is able to promote osteoblastic cells activity, resulting in the enhanced bone ingrowth. Materials and Methods: Pulsed laser deposition (PLD) method was used for coatings preparation. For depositions, Si-HAp targets (1.4 wt % of Si), made up from nanopowders synthesized by wet method, were used. Results: Microstructural and mechanical properties of the produced coatings, as a function of substrate temperature, were investigated by scanning electron and atomic force microscopies, X-ray diffraction, Fourier transform infrared spectroscopy, and Vickers microhardness. In the temperature range of 400-600°C, 1.4-1.5 µm thick Si-HAp films, presenting composition similar to that of the used target, were deposited. The prepared coatings were dense, crystalline, and nanostructured, characterized by nanotopography of surface and e...

Nanomagnetism: Fundamentals and Applications, C. Binns Ed., Elsivier, 2014

Magnetic nanostructures are characterized by a wide variety of geometries, which cover the range ... more Magnetic nanostructures are characterized by a wide variety of geometries, which cover the range from granular bulk materials to low-dimensional magnetic systems, such as nanoparticles, nanowires/nanotubes, granular/continuous thin films and multilayers, dots, etc. The magnetic behaviour of ensembles of magnetic entities depends on their intrinsic magnetic properties and many other factors, including short and long range magnetic interactions. The chapter focus on the effect of interactions in assemblies of single-domain nanoparticles, each of them being considered as a “superspin” with a magnetic moment related to the particle volume. Depending on the type and the strength of the interactions among the magnetic entities, the magnetic behavior of an assembly of super spins evolves from ferromagnetic-like behavior to paramagnetic-like behaviour, through spin glass like behaviour. Due to the enhanced time and magnetization scale with respect to atomic systems, the suffix super has bee...

Journal of Magnetism and Magnetic Materials, 2014

Current magnetic recording media using perpendicular CoCrPt-Oxide granular films are reaching the... more Current magnetic recording media using perpendicular CoCrPt-Oxide granular films are reaching their physical limit (approx 750 Gbit/in2 density) due to thermal fluctuations that hinder a further reduction of grain size (<6–7 nm) needed to scale down the bit size. L10-FePt alloy is currently considered the most promising candidate for future recording media with areal densities above 1 Tbit/in2 thanks to its high magneto-crystalline anisotropy (K=6–10 MJ/m3), which enables it to be thermally stable even at grain sizes down to 3 nm. However, its huge anisotropy implies an increase of the switching field, which cannot be afforded by current available write heads. To simultaneously address the writability and thermal stability requirements, exchange coupled composite media, combining two or multiphase hard and soft materials, where the hard phase provides thermal stability and the soft phase reduces the switching field, have been recently proposed. This paper briefly reviews the fund...

Thin Solid Films, 2013

ABSTRACT In the present work, the Si-HAp coatings were deposited on titanium substrates by Pulsed... more ABSTRACT In the present work, the Si-HAp coatings were deposited on titanium substrates by Pulsed Laser Deposition technique. For deposition, the Si-HAp targets (1.4 wt% of Si), produced starting from wet synthesised powders, were used. The properties of coatings were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy and Vickers microhardness. The obtained Si-HAp coatings presented a nanosized structure, proper thickness and hardness for applications in orthopedical and dental surgery, aimed at improving the stability and the osteointegration of bone implants.

IEEE Transactions on Magnetics, 2002

Superlattices and Microstructures, Aug 31, 2009

Structural and magnetic properties of nanocomposites of ferrimagnetic (CoFe2O4) and antiferromagn... more Structural and magnetic properties of nanocomposites of ferrimagnetic (CoFe2O4) and antiferromagnetic (NiO) nanoparticles with different percentages of cobalt ferrite (50% and 15% wt) have been studied. The observed Exchange Bias properties and their dependence on interparticle interactions are discussed.

Journal of Magnetism and Magnetic Materials, 2012

We have studied the Exchange Bias (EB) effect in nanocomposite films consisting of Fe nanoparticl... more We have studied the Exchange Bias (EB) effect in nanocomposite films consisting of Fe nanoparticles (mean size ~1.9 nm) embedded in an antiferromagnetic Mn matrix. They were produced by co-deposition through a gas aggregation cluster source and molecular beam epitaxy and have different Fe volume filling fractions (2.2\% and 24.8\%). The exchange field, higher in the sample with higher Fe concentration (at T=5 K, Hex~460 Oe for 24.8\% and ~310 Oe for 2.2\% ), in both the samples decreases with increasing T, finally disappearing at T~40 K. The EB properties have been studied in conjunction with results on the thermal dependence of the magnetic coercivity, zero-field-cooled and field-cooled magnetization and thermoremanence. The different Fe content strongly affects the magnetothermal properties, featuring superparamagnetic relaxation in the diluted sample and a reentrant ferromagnet-type transition in the concentrated one. Hence, the EB properties of the two samples have been discusse...