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Addis Ababa University Libraries Electronic Thesis and Dissertations: AAU-ETD! >
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http://hdl.handle.net/123456789/88
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| Title: | THE STUDY OF ANTIFERROMAGNETISM IN DILUTED MAGNETIC SEMICONDUCTOR ”CDMNTE” |
| Authors: | Gebru, Tadesse |
| Date Added: | 6-Sep-2007 |
| Abstract: | 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 diluted
magnetic semiconductors (DMS) in which small quantity of magnetic ion is introduced
in to normal semiconductors. The first known such DMS are II-VI and III-V semiconductors
diluted with magnetic ions like Mn, Fe, Co, Ni, etc. Most of these DMS exhibit
very high electron and hole mobility and thus useful for high speed electronic devices.
CdMnTe systems with face centered cubic structure and long-range antiferromagnetic
ordering is investigated with in the frame work of the Heisenberg model.
The Hamiltonian includes exchange interactions with the nearest neighbors and Zeeman
terms. Calculations are performed using Holstein-Primakoff transformation and
Green’s function formalism. Temperature dependencies of the spin-wave specific heat
and reduced magnetization are determined. In addition to these linear concentration
dependence of Neel temperature is also predicted.
The spin-wave energy shows T4 temperature dependence, where as the predicted
magnon part the heat capacity is proportional to T3 which is similar to the Debye
phonon heat capacity. The sublattice magnetization decreases quadratically with
temperature in the low-temperature region. But the dependence of the Neel temperature
on the manganese ion concentration is linear. All the findings are in broad
agreement with experimental observations. |
| Description: | A THESIS PRESENTED TO
THE SCHOOL OF GRADUATE STUDIES
ADDIS ABABA UNIVERSITY
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF
MASTER OF SCIENCE in PHYSICS |
| URI: | http://hdl.handle.net/123456789/88 |
| Appears in: | Thesis - Physics
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