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Negative Dynamic Resistance and RF Amplification in Magnetic Tunnel Junctions
Hiroyuki Tomita,Hiroki Maehara,Takayuki Nozaki,Yoshishige Suzuki 한국자기학회 2011 Journal of Magnetics Vol.16 No.2
We report on a numerical calculation study of two new functional properties in magnetic tunnel junctions (MTJs), negative dynamic resistance and RF amplification. The magnetic dynamics in a conventional CoFeB/MgO/CoFeB MTJ with in-plane magnetization was investigated using a macro-spin model simulation. To examine the influence of thermal fluctuations, random external magnetic fields were also included. Using a voltage controlled bias circuit, the negative dynamic resistance was obtained from time averaged Ⅰ-Ⅴ characteristics at both 0 K and 300 K under appropriate external magnetic fields and bias voltages. Using this negative dynamic resistance property, we demonstrated RF amplification with a 100 ㎒ high frequency signal. Sizable RF amplification gain was observed without thermal fluctuation. However, at 300 K, the RF signal was not amplified because low frequency magnetization dynamics were dominant.