Magneto-transport properties of GaMnAs based trilayer structures
- 주제(키워드) magneto-transport , trilayer , GaMnAs
- 발행기관 고려대학교 대학원
- 지도교수 이상훈
- 발행년도 2009
- 학위수여년월 2009. 8
- 학위명 석사
- 학과 일반대학원 물리학과
- 세부전공 고체물리학전공
- 원문페이지 51 p
- 실제URI http://www.dcollection.net/handler/korea/000000008911
- 본문언어 영어
- 제출원본 000045551812
초록/요약
We have performed magneto-transport measurements on the a series of (Ga,Mn)As/(In,Ga)As/(Ga,Mn)As trilayer structures with different thicknesses of (In,Ga)As spacer layers. The (Ga,Mn)As layers in the top and bottom of the structure have 2.7 % and 3.8 % Mn composition, respectively, which leads slightly different magnetic properties between two layers. The thicknesses of (In,Ga)As spacer layer varies from 5 to 50 nm in the series. The magneto-transport measurements have been carried out in different two geometries, in which external fields are applied in-plane and out-of plane, respectively, to the sample. Magnetic anisotropy fields obtained from angle dependence of hall measurement shows systematic change with barrier thickness in the series. While the sample with 5 nm spacer layer exhibits dominant in-plane magnetic anisotropy, it systematically changes to out-of-plane as the spacer layer thickness increases to 50 nm. This phenomenon results from the increasing of tensile strain on the (Ga,Mn)As by increasing (In,Ga)As spacer layer thickness. And we also measured critical sample contained 10 nm InGaAs layer at different temperature varied 10 K to 40 K. Magnetic anisotropy fields shows dominance of the magnetic anisotropy changed from out-of-plane to in-plane. This phenomenon also resulted from strain on the GaMnAs layer by InGaAs layer. Lattice’s mismatch was caused from difference of GaMnAs layer’s lattice parameter, and InGaAs layer’s lattice parameter at difference temperature.
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ABSTRACT 1
CONTENTS 3
FIGURES 5
CHAPTER 1 Introduction 10
CHAPTER 2 Theoretical background 10
2.1 Hall effect in ferromganetic material 10
2.2 Magnetic Anisotropy of ferromagnetic thin films 13
2.2.1 Stoner-Wolfarth model 13
2.2.2 Magnetic Anisotropy of GaMnAs ferromagnetic material 15
2.2.3 Scheme of freeenergy density 19
2.2.4 Effective anisotropy barrier 21
CHAPTER 3 Sample preparation and measurement 23
3.1 sample growth : Molecular Beam Epitaxy (MBE) 23
3.2 Magneto-transport measurement 24
3.2.1 Wet etching 24
3.2.2 DC measurement 36
CHAPTER 4 Result and discussion : GaMnAs layer's Magnnetic properties with InGaAs layer 28
4.1 Thickness dependence of InGaAs spacer layer 28
4.1.1 Magnetotransport measurement 32
4.1.2 Magnetic anisotropy 34
4.1.3 Effective anisotropy barrier, scheme of free energy density 37
4.2 Temperature dependence of critical state 37
4.2.1 Magneto-transport measurement 37
4.2.2 Effective anisotropy barrier, scheme of free energy density 40
CAPTER 5 Summary and Conclusion 45
REFERENCES 46
