(A) micromagnetic study on the critical current density of spin transfer torque = 스핀전달토크의 임계전류밀도에 관한 미소자기학적 연구

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A great deal of research on spin transfer torque has been carried out for a decade, since it was initiated by the predictions of Slonczewski and Berger in 1996. It provides a novel means to manipulate the magnetization by electric current itself, not by the magnetic field it induces. As well as its rich physics we have to explore, spin transfer torque has high potential for important applications such as write scheme in Magnetic Random Access Memory (MRAM), spin torque nano-oscillator, and memory device using domain wall motion. One important issue in the research field of spin transfer torque is to lower the critical current density for the excitation of magnetization. The critical current density is too high for practical use, so that the reduction of the current is needed. In this dissertation, we study variations of critical current density for magnetization switching in high density MRAM cell arrays with longitudinal magnetization. Also, the critical current density for domain wall motion in nanowire with perpendicular anisotropy as a function of nanowire geometry is studied, and perpendicular magnetic tunnel junction (MTJ) with soft polarization-enhancement layers as function of saturation magnetization and interlayer exchange coupling strength. In the first part, we investigate the change of the switching current density in the conventional rectangular MRAM cell array. When the cell spacing is within substantial magnetostatic interaction, the magnetostatic interaction has two different kinds of effect on the switching current density. First, the overall stray field from the neighboring cells increases or decreases the switching current density, according to the relative direction of the switching to the stray field. It follows the theoretical description using single domain model. The other one is the increase of the switching current density due to the resonant precession of the magnetic cells, regardless of the switching direction. It becomes problem...
Advisors
Lee, Taek-Dongresearcher이택동researcher
Description
한국과학기술원 : 신소재공학과,
Publisher
한국과학기술원
Issue Date
2009
Identifier
327757/325007  / 020037128
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 신소재공학과, 2009. 8., [ ix, 90 p. ]

Keywords

spin transfer torque; micromagnetics; critical current density; 스핀전달토크; 미소자기학; 임계전류밀도

URI
http://hdl.handle.net/10203/49726
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=327757&flag=dissertation
Appears in Collection
MS-Theses_Ph.D.(박사논문)
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