Micromagnetic Investigation of Magnetization Reversal in Sphere-Shaped Ferromagnetic Nanoparticle

In this paper, the magnetization reversal of sphere-shaped ferromagnetic nanoparticles has been investigated by means of micromagnetic simulation. Some ferromagnetic particles such as Cobalt, Iron, Nickel, and Permalloy were modeled with size variation from 50 nm to 100 nm. The discretization of the ferromagnetic model was used a cell size of 2.5×2.5×2.5 nm3 considering the exchange length (lex) of the materials. The quasi-static magnetic field was induced into the nanosphere to observe the magnetization response under time dependence. It is found that the coercivity values are decreased as the sphere size increased, which was conformed the experimental results. It is also observed that the domain structure of a single particle in remanent and ground-state condition are identical. Therefore, the specific understanding of magnetization process and domain structures in ferromagnetic nanoparticles could be an important step in the development of nanopatterned magnetic memory storage.

SPREAD OF INTERACTION IN NANOCOMPOSITE HARD/SOFT NANOSTRUCTURED MAGNETS

In this study, the magnetic properties of 3D modeled two-phase hard/soft nanocomposite nanostructured magnets were simulated by means of the Monte-Carlo method. The dependences of the energy product and coercivity on the grain size and magnetically soft phase content were investigated. The influence of the interaction spreading in the soft phase on the magnetic properties was also discussed. The obtained results revealed that the energy product reaches an optimal value when the soft phase content ranges around 50 vol.%, and a strong magnetic interaction spreading locally along the Kneller-Hawig exchange length seems to be more important than a weak but widely spreading interaction.

Outsourcing: two case studies from the Victorian public hospital sector

Outsourcing was one process of privatisation used in the Victorian public health sector in the 1990s. However it was used to varying degrees and across a variety of different services. This paper attempts to answer the questions: Why have managers outsourced? What have managers considered when they have decided to outsource? The research was carried out in a rural hospital and a metropolitan network in Victoria. The key findings highlight the factors that decision makers considered to be important and those that led to negative outcomes. Economic factors, such as frequency of exchange, length of relationships between the parties, and information availability, were often ignored. However, other factors such as outcome measurability, technology, risk, labour market characteristics and goal conflict, and political factors such as relative power of management over labour were often perceived as important in the decision-making process. Negative outcomes from outsourcing were due to the short length of relationships and accompanying difficulties with trust, commitment and loyalty; poor quality; and excessive monitoring and the measurement of outcomes.

Coercivity in nanostructured FeCo-based powders prepared by mechanical alloying

FeCo-based nanostructured powders were prepared by mechanical alloying and subsequently heat treated in an attempt to reduce their coercivity, HC. Although the powders had grain sizes smaller than the magnetic exchange length, a low HC, as expected from Herzer's model, did not occur. The results of magnetic measurements on dilute and concentrated samples of the powder, as well as measurements of the temperature dependence of the magnetic properties from 10-300 K, indicate that the degree of magnetic interaction between the individual powder particles determines the relatively high HC of 10-20Oe at room temperature.

MICROMAGNETICS OF THIN SHELLS

We study a thin-shell limit of micromagnetic energy for soft small ferromagnets. The relations between thickness of the magnet t, diameter l and magnetic exchange length w are t/l → 0 and tl/w2 ≲ 1. We prove a Γ-convergence of the original 3D problem to a nonlocal 2D problem.