New advances on Au–magnetic organic hybrid core–shells in MRI, CT imaging, and drug delivery

Magnetic nanoparticles have been studied for scientific and technological applications such as magnetic storage media, contrast agents for magnetic resonance imaging, biolabelling, separation of biomolecules, and magnetic-targeted drug delivery.

Structural Properties of Fe/Cu Magnetic Multilayers: A Monte Carlo Approach

Using atomistic Monte Carlo simulations, we investigated the impact of the interface on the structural properties of iron and copper (Fe/Cu) magnetic multilayers grown by Voronoi diagram. Interest in magnetic multilayers has recently emerged as they are shown to be promising candidates for magnetic storage media, magneto-resistive sensors and personalized medical treatment. As these artificial materials show large differences in properties compared to conventional ones, many experimental and theoretical works have been dedicated on shedding light on these differences and tremendous results have emerged. However, little is known about the influence of the interfaces on magnetic layers. Using numerical approaches, we show that the structure of each layer depends on its thickness and the interface morphology. The Fe and Cu layers can adopt either the body-centered-cubic (bcc) or face-centered-cubic (fcc) structure, while the interface can assume amorphous, bcc, fcc, or a mixture of bcc and fcc structures depending on the layer thicknesses. These results are in good agreement with the experiments. They could be helpful in understanding effects such as giant magneto-resistance from the structural perspective.

Thickness Dependence of Magnetic Switching Dynamics of Barium-Ferrite as A High-Density Perpendicular Magnetic Storage Media

Micromagnetic study of material thickness dependence of Barium-ferrite nano-dot magnetization dynamics has been performed. The used materials characteristics in this research represent the properties of Barium-ferrite. Barium-ferrite was modeled as a nano-dot with a surface area of 50 50 nm2 and its thickness varies from 5 nm to 100 nm. This nano-dot was simulated using micromagnetic simulator software by solving Landau-Lifshitz-Gilbert equation. According to this study, obtained that the Barium-ferrite nano-dot has excellent thermal stability. Magnetization rate of this nano-dot decreases exponentially with the increase of thickness. The fastest magnetization rate observed in 5 nm of nano-dot thickness, meanwhile 45 nm for the slowest rate. Magnetization reversal mode of this Barium-ferrite nano-dot is dominated by domain wall nucleation and propagation. During the propagation of the domain wall, the exchange interaction becomes the main aspect compared to the other contributed energies.

The Influence of Bath Concentration on Particle Size of Cobalt Nanoparticles

Cobalt nanoparticles have been widely used in magnetic storage media application. This study reports the characteristic and properties of Cobalt (Co) nanoparticles due to the effect of different bath concentrations. The Co nanoparticles were coated on the stainless steel substrate using different molar concentrations (M) of 0.05 M, 0.075 M and 0.1 M, respectively. The coating was done using electrodeposition method. Interestingly, the sphere particles surrounded by flakes were only found in the Co nanoparticles prepared in 0.075 M. This structure exhibited the smallest particles size, which is 83 nm. Besides, the nanoparticles also had the highest microhardness if compared to the Co nanoparticles prepared in 0.05 M and 0.1 M. The Co nanoparticles prepared in other concentrations were irregular structure without flakes. The polarization curves for all the nanoparticles showed the active behaviour without any distinctive to passivation. However, the corrosion rate of the sample prepared in 0.075 M was the lowest; 42.51 mpy compared to the other samples prepared in 0.05 M and 0.1 M, which were 176 mpy and 223.3 mpy, respectively. Hence, it was found that the bath concentrations affect the particle size of as-synthesized Co nanoparticles and finally changed the properties of final product.

Atomic Ordering in Nano-layered FePt: Multiscale Monte Carlo Simulation

Combined nano- and mesoscale simulation of chemical ordering kinetics in nano-layered L10 AB binary system was performed. In the nano- (atomistic) scale Monte Carlo (MC) technique with vacancy mechanism of atomic migration was implemented with diverse system models. The mesoscale microstructure evolution was, in turn, modeled by means of MC procedure simulating antiphase boundary (APB) motion as controlled by APB energies evaluated within the nano-scale simulations. The study addressed FePt thin layers considered as a material for ultra-high density magnetic storage media and revealed metastability of the L10 c-variant superstructure with monoatomic planes parallel to the (001) free surface and off-plane easy magnetization. The layers, initially perfectly ordered in the L10 c-variant, showed homogenous disordering running in parallel with a spontaneous re-orientation of the monoatomic planes into a mosaic-microstructure composed of L10 a- and b-variant domains with (100)- and (010)-type monoatomic planes, respectively. The domains nucleated heterogeneously on the Fe free surface of the layer, grew discontinuously inwards its volume and finally relaxed generating an equilibrium microstructure of the system. Two �atomistic-scale� processes: (i) homogenous disordering and (ii) nucleation of the L10 a- and b-variant domains showed characteristic time scales. The same was observed for the meso-scale processes: (i) heterogeneous L10 variant domain growth and (ii) domain microstructure relaxation. The above phenomena modelled within the present study by means of multiscale MC simulations have recently been observed experimentally in epitaxially deposited thin films of FePt.

Compositional Evolution of FePt Nanoparticles Prepared by Different Organometallic Synthesis Routes

Self-assembled FePt nanoparticle arrays are candidate structures for ultrahigh density magnetic storage media. One of the factors limiting their application to this technology is particle-to-particle compositional variation. In the present study, an analysis is provided for the formation mechanism of FePt nanoparticles synthesized from the thermal decomposition of Fe(CO)5 and the reduction of FeCl2 by superhydride. In both processes, Pt rich seeds initially form from the reduction of Pt acetylacetonate. The particle formation mechanism has been studied by extracting particles at different stages of the synthesis and individually determining particle-to-particle composition by STEM-XEDS. In the case Fe(CO)5, the Fe is gradually incorporated into the Pt seeds and produces a wide variation in compositional distribution about the mean value. In contrast, the FeCl2 has a nearly instantaneous shift in composition to the average value with the introduction of the superhydride reducing agent. The discrepancies in compositional uniformity between the two processes will be discussed in terms of the intrinsic differences between the different precursors.