Browsing by Author "Solomon, Yared"

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    The Study of Ferro and Antiferromagnetism in Diluted Magnetic Semiconductor GaMnAs
    (Addis Ababa University, 2010-06) Solomon, Yared
    The prospect of a new generation of electronic devices based on the fundamental quantum property of angular momentum, known as spin, has led to the rapidly developing field of spintronics. . These materials are created by using molecular beam epitaxy (MBE) to incorporate into traditional semiconductors a quantity of transition metal atoms sufficient that ferromagnetism is exhibited. We present first principles calculations for prospective magnetic materials for future applications in spintronics. The material studied is focused on dilute magnetic semiconductors (DMS) like Ga1−x Mnx As that play a key role in semiconductor spintronics. Due to their ferromagnetic properties they can be used in magnetic sensors and as spin injectors. The basic problem for applications are, however, the relatively low Curie temperatures of these systems. We therefore focus on understanding the magnetic properties and on a reliable calculation of Curie temperatures from first principles. We have developed a theoretical framework for calculating critical temperatures by combining first principles calculations and in terms of the Ruderman– Kittel–Kasuya–Yosida quantum spin model in Green’s function approach. Random distributions of the magnetic atoms are treated by using an analytical average of magnetic configuration are performed using green function formalism using the dispersion relation for k2 for antiferromagnetic case and k for ferromagnetic case . temperature dependencies of the spin wave specific heat,inverse magnetic susceptibility and reduced magnetization are determined .the result shows T 3 2 dependence of for magnon specific heat in ferromagnetic case and formulaformula T3 in antiferomagnetic,the dependence of the Neel temperature on the manganese ion concentration is linear thus for our calculation the highest Neel temperature obtained T=36.5k with in the concentration of 0.05 ,the reciprocal susceptibility increases linearly with increasing temperature above 173k