Magnetic-doped ZnO diluted magnetic semiconductors First-principles calculations

Title: Magnetic-doped ZnO diluted magnetic semiconductors First-principles calculations Author: LIANG Pei Degree-granting units: Huazhong University of Science and Technology Keywords: Spintronics;; ZnO;; magnetic semiconductor;; co-doping technology;; first-principles calculations;; electronic structure;; Monte Carlo method
;; Curie temperature Abstract:
Spintronics is the use of electronic neodymium magnets charge and spin two degrees of freedom as an information carrier, so as to realize information transmission, processing
And storage, has become the electronics, physics and materials research in the interdisciplinary one of the hot, dilute magnetic materials as a key
Semiconductor research concern. View of the zinc oxide semiconductor material as the parent diluted magnetic semiconductors is possible to achieve a high doping concentration
And the doping ion 3d band can be intrinsic defect states and produce a strong ferromagnetic coupling. Therefore, ZnO diluted magnetic semiconductors
Preferred research system. Combined with a high Curie temperature for the analysis of dilute magnetic semiconductors and diluted magnetic semiconductor production mechanism within the magnetic
The two key scientific issues, this paper is mainly based on first-principles density functional calculation of diluted magnetic semiconductor ZnO electronic structure
And analysis and interpretation of its mechanism of magnetic origin. On this basis, research and first-principles Monte Carlo method to calculate the coupled integration
ZnO diluted magnetic semiconductors, the http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php Curie temperature, Curie temperature of the control methods, focusing on different single system for the undoped and doped ZnO
Dilute magnetic semiconductors and magnetic properties of the mechanism.
First, to clarify the use of first-principles pseudopotential plane-wave method and the full potential -
Augmented plane wave method ZnO diluted magnetic semiconductor based electronic structure theory and calculation program, from the perspective of oxide magnetic band
Of semiconductor transition metal coupling, the mechanism to explain the basis of magnetic origin. Further use of first-principles and Monte
Carlo coupled integration algorithm to predict the Curie temperature of different computing systems to study the regulation and control methods.
Secondly, the use of full potential
- Linearized augmented plane wave method in the generalized gradient approximation calculations of the carbon-doped ZnO single electronic structure. The results show that carbon-doped In-O-
Home or in the magnetic gap position will lead and whether it is interstitial doping or doping system has replaced half metallic,
Theoretically has a high spin polarization. Using first-principles and Monte Carlo methods to obtain the coupled carbon-doped ZnO Curie
Temperature at different doping concentrations, the Curie temperature between 251 ~ 439 K distribution. It is suggested that a single carbon-doped ZnO diluted magnetic semiconductors
In a suitable preparation conditions, can be ferromagnetic at room temperature.
Use the full potential - linearized augmented plane wave method in the Coulomb potential repair
Is, the calculation of the neodymium-doped ZnO and its single, respectively, with a V_ (Zn) and a V_o electronic structure and magnetic properties. That contains
V_ (Zn) deficiencies of neodymium-doped ZnO may have a higher Curie temperature, without any intrinsic defects showed a paramagnetic, with
There V_o system with weak antiferromagnetic coupling. For with V_ (Zn) deficiencies of the system of its magnetic origin, the use of bound polaron mechanism
Accordingly interpreted.
Finally, the study of transition metal - metal doped ZnO diluted magnetic semiconductor systems for the effects of sub-
Analysis of the magnetic exchange interaction of carriers generated regulatory mechanism. Studied the Co-Al-doped ZnO system, through the introduction of Al atoms to achieve a total
Anti-doping system ferromagnetic to ferromagnetic transition. Mainly due to the origin of ferromagnetism under the control of unwanted e-e-Al-2p and neighbor
The Co-3d electron interaction, leading to a system of magnetic interactions in line with its carrier-control pd exchange model. Fe-Al
The calculations show that the doped ZnO system, Fe-doped ZnO system in the ground state shows antiferromagnetic, when the introduction of Al atoms, Al is the most
Neighbor Fe-doped ZnO doping system is to achieve a state of the antiferromagnetic to ferromagnetic transition, this time Al-2p electrons and Fe-3d electrons do not occur as
Used, the production of ferromagnetic long-range exchange interaction is RKKY.
Studied the Cu-N transition metal - nonmetal doped ZnO dilute magnetic semiconductor body
Department of carrier-control mechanism, through the introduction of N atoms, N-2p and Cu-3d exchange interaction occurred, the exchange interaction makes the doped system
System more stable. Both before and after the doping, the system is still top of the valence band are occupied O-2p electron in the conduction band top in the Cu-3d e
And 4s electrons to occupy most of the state. Carrier-control model is used to explain the origin of magnetism, due to the incorporation of N makes the body doping
Lines to increase the number of carriers, magnetic ion exchange interaction between free carriers through is passed, leading to a system of magnetic ordering
.
Further study of the transition metal - non-metallic co-doped system the Curie temperature control method and mechanism. Mn-N that were
Doping in the success achieved under the ferromagnetic ground state transition. From the Heisenberg model and mean field theory and the first use of Monte Carlo
Principle of the method of co-doped system can be predicted with room temperature ferromagnetism.
In short, by first-principles and Monte Carlo
Coupled integration method to calculate the single-doped and codoped several typical system, indicating that its mechanism is different, which explains the rare
The origin of magnetic semiconductors and magnetic Curie temperature (T_c) to improve the channels for doped ZnO diluted magnetic semiconductor design process provides a practical side
To. Degree Year: 2009