The Study of Ferro and Antiferromagnetism in Diluted Magnetic Semiconductor GaMnAs
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Date
2010-06
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Addis Ababa University
Abstract
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
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Ferro and Antiferromagnetism