Study of Ferromagnetism in a new High Tc Ferromagnetic Semiconductor K2(S; Ge) without Transition Metal Element
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Date
2007-03
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Addis Ababa University
Abstract
In the present work we have studied the ferromagnetic properties of a high temperature
magnetic semiconductor K2S(Si=Ge) which is free from any transition metal
element. A model Hamiltonian taking into account, the exchange interaction of conduction
electrons with localized electrons coming from Si/Ge and the host is studied
using quantum field theory formalism of Green functions and also using spin wave
theory to find expression for Curie temperature, TC, magnetic susceptibility, Â and
specific heat capacity of magnons excited. Tc,Â, and C are plotted with concentration
of dopants (Si/Ge). The direct proportionality relation of the Curie temperature, Tc
and concentration, x of Ge in K2(S; Ge) have been shown. The reduced magnetization
vs the reduced temperature graph has been plotted. The plot shows convex
curvature. The heat capacity vs temperature has also been plotted. The plot has got
parabolic curve nature for low concentration, x = 0:02 and become linear for high
concentration, x > 0:08, which are in good agreement with available experiments.
We also plotted the graph for the reciprocal of the susceptibility versus temperature
difference. As can be seen from the graph the material is in its ferromagnetic state
for T < 299:9K. And (1=Â) = 0 at T = TC = 300K, and the graph is straight line
after T = 300K. Which shows the material leaves its ferromagnetic state for T = TC.
Which are in good agreement with available experiments
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Keywords
Study of Ferromagnetism