THE STUDY OF FERROMAGNETISM IN DILUTED MAGNETIC SEMICONDUCTOR GaMnAs

Abstract

In the present work we have studied the ferromagnetism properties of dilute magnetic semiconductor i.e GaMnAs which is depends on transition metal element(Mn). 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 the field of spintronics. These materials are created by using Molecular beam of epitaxy to incorporate into traditional semiconductors a quantity of transition metal atoms sufficient that ferromagnetism is exhibited. The material studied is focused on DMS like Ga1−xMnxAs that play a key role in semiconductor spintronics. Most of the semiconductor materials are diamagnetic by nature and therefore cannot take active part in the operation of the magneto-electronic devices. In order to enable them to be useful for such devices efforts have been made to develop DMSs in which small quantity of magnetic ion is introduced in to normal semiconductors. Most of these DMS exhibit very high electron and hole mobility and thus useful for high speed electronic devices. GaMnAs systems with Fcc structure and long-range FM ordering is investigated with in the frame work of the Heisenberg Hamiltonian model. A model Hamiltonian taking into account, the exchange interaction of conduction electrons with localized electrons coming from Mn ion and the host is studied using quantum field theory, formalism of Green’s function as well as Calculations are performed using Holstein-Primakoff transformation to find expression for Curie temperature (TC), magnetic susceptibility (cm) and specific heat capacity of magnon excited, Curie temperature (TC) and magnon heat capacity (Cmag) are plotted with concentration of dopants (Mn) ion.The heat capacity Vs temperature has also been plotted. The plot has got parabolic curve nature for low xm = 0:05 and become linear for high xm > 0:08, which are in good agreement with available experiments. The reduced magnetization Vs the reduced temperature graph has been plotted. The plot shows convex curvature for low Mn impurity. The direct proportionality relation of the Curie temperature TC and concentration, (xm) of Mn in GaMnAs have been shown. We also plotted the graph for the reciprocal of the magnetic susceptibility versus temperature difference. As can be seen from the graph the material is in its FM state for T < 173K. And (c1 ) = 0 at T = TC = 173K, and the graph is straight line after T = 173K. Which shows that the material leaves its FM state for T = TC. Which are in good agreement with available experiments