Browsing by Author "Feseha Abrham"

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    Study of Magnetization and Critical Temperature for Nanomagnetic Particles
    (Addis Ababa University, 2011-06) Feseha Abrham; P. Singh (Professor)
    Magnetic nanostructures, such as dots and dot arrays, nanowires, multilayers and nano- junctions, are reviewed and compared with bulk magnets. By using the Gibbs free energy variational principle based on the Bogoliubov inequality the magnetic properties and crit- ical behavior of metallic nanoparticles having concurrently atomic disorder, dilution and competing interactions, are studied within the framework of an Ising model. As a case of study we have considered the Fe0:5Mn0:1Al0:4 alloy characterized for exhibiting, un- der bulk conditions, low temperature reentrant spin glass (RSG) behavior and for which experimental and simulation results are available. Our results allow concluding that the variational model is successful in reproducing features of the dependence of the critical temperature with particle size and low temperature magnetization reduction consistent with a RSG behavior. In this work we compute the magnetization per site and the mag- netic susceptibility, as a function of temperature, for di erent values of the coordination number