透過磁偶極交互作用同步奈米自旋力矩振盪器

Synchronization of Spin Torque Nano-Oscillators through Dipolar Interactions

陳浩軒(Hao-Hsuan Chen)

指導教授 ： 張慶瑞

國立臺灣大學/理學院/物理研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.03074

摘要

近年來，自旋閥系統已被理論和實驗證明為自然界中最小的自發振盪元件。透過巨磁阻效應，這種形式的運動能產生出高頻率的電子微波震盪訊號，因此這樣的系統(稱為奈米自旋振盪器，STNO)可能成為未來通訊的要角之一。但單個STNO 能提供的功率過小，所以最直接的做法就是透過串並聯大量的STNO，並且利用各個STNO 本身的巨磁阻訊號來對陣列中其他所有自旋閥進行耦合促使所有
的STNO 同步發出振幅被加成的振盪訊號。

在我們的工作裡，主要透過垂直型STNO 陣列中各自由鐵磁層間存在的磁偶極交互作用來形成同步化。而理論分析方面，我們將本著于自由層中存在強大去磁場的事實建立一個近似理論，並從中得到同步垂直型STNO 所需的相應條件。該理論亦明確指出，垂直型STNO 不可能如前述那樣可由巨磁阻訊號的回饋來使陣列中所有的STNO 產生同步進動。最後，我們利用巨觀自旋模型 (Macrospinmodel) 的數值結果驗證我們的理論分析。

關鍵字

自旋閥 ； 奈米自旋力矩振盪器 ； 自旋力矩振盪器的同步

並列摘要

Recently, spin-valve has been shown as a smallest self-oscillation device in theory
and experiment. Through Giant magnetoresistance (GMR) effect, such a
self-oscillation mode can be converted into an electric microwave oscillating signal.
Therefore, the spin-valve which is called spin-torque nano-oscillator, i.e. STNO can be one of the essential rules of commutations in the future. However, because the output power of a single STNO is too small, the way to solve is making multi STNOs be connected serially or parallel in circuits and coupled them with GMR feedbacks which come from every STNOs in the array to induce synchronization and enhance the amplitudes of microwave signals.

In our work, we use the dipolar interaction between the free layers of PERP STNOs
in the array to induce synchronization. In theoretical analysis, due to the strong
demagnetization of the free layer, an approximate theory can be obtained. And in such an analysis, the condition for the synchronization of PERP STNOs can be obtained. This theory also point out definitely that it is impossible to synchronize PERP STNOs through microwave signals feedback from GMR effect. At last, the numerical simulation results from Macrospin model will be given to verify our theoretical
analysis.

並列關鍵字

spin valve ； spin torque nano-oscillator ； synchronization of spin torque nano-oscillator

參考文獻

[31] H. H. Chen, J.H. Chang, and C. R. Chang, SPIN,1,1(2011)

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