Frequency-Locking in Serially Coupled Spin Transfer Nano-Oscillators
- Frequency-Locking in Serially Coupled Spin Transfer Nano-Oscillators
- 박재현; 박승영; 민병철; 신경호
- Spin transfer nano-oscillators; Magnetic tunnel junctions
- Issue Date
- 2011년도 하계학술연구발표회 (한국자기학회)
- More recently, the characteristics of microwave emission by spin torque induced magnetization precession in magnetic tunnel junctions (MTJ) have extensively been examined for radio frequency (rf) device applications . Although the spin-transfer nano-oscillators (STNO) can present such an excellent frequency tunability in the GHz range and fully compatible with a high level of integration, there are two main drawbacks regarding the weak output power and broad spectral linewidth of the generation signals . One of the solutions to overcome these problems is to synchronize many STNO devices by use of various local or non local mechanisms .
As one of the non local methods, we study on the interaction between electrically connected STNOs through spin transfer self-emitted microwave current. The fabricated device consists of a nominally 100 X 60 nm2 elliptical nanopillar structure composed of SiO2 substrate/Ta (5)/CuN (30)/Ta (5)/Pt37Mn63 (20)/Co70Fe30 (3)/Ru (0.8)/Co60Fe20B20 (5)/MgO (1)/Co60Fe20B20 (2)/Ta (10)/CuN (10)/Ru (7) (in nm). The STNO has the tunnel magnetoresistance (TMR) of 63 % and resistance-area (RA) product of 5 Ω·μ㎡ in the parallel state. With respect to the microwave measurement, the device is connected to a ground-signal-ground (GSG) probe with coplanar waveguide (CPW) pattern. And the rf output spectra are monitored by a spectrum analyzer through the bias-tee circuit including a DC bias input and a rf output signal port. The output signals are amplified by a 40 dB preamplifier, but both the amplification and background noise are subtracted for the presented data. All measurements are carried out at room temperature.
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