Mutual phase-locking of microwave spin torque nano-oscillators
Mutual phase-locking of microwave spin torque nano-oscillators
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DOI：
10.1038/nature04035
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发表时间：
2005-09-15
期刊：
影响因子：
64.8
通讯作者：
Katine, JA
中科院分区：
文献类型：
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作者：
Kaka, S;Pufall, MR;Katine, JA
在纳米级磁性多层器件中发生的自旋扭矩（1，2）效应可用于响应直流电流产生稳态微波信号（3-8）。这为更常用作磁场传感器和磁存储器元件（9）的磁电结构建立了新的功能。目前，从单个自旋扭矩纳米振荡器（STNO）发射的微波功率通常小于1 nW。为了实现更有用的功率水平（微瓦量级），器件可以由相位相干STNO阵列组成，其方式类似于约瑟夫森结阵列和更大的半导体振荡器（10-12）。在这里，我们展示了两个紧密靠近的STNO相互锁相-也就是说，它们同步，这是相互作用的非线性振荡器系统的一般趋势（13-15）。锁相状态是独特的，其特征在于信号线宽突然变窄，并且由于各个振荡器的相干性而增加功率。锁相STNO阵列可用作纳米级基准振荡器。此外，阵列元件（相控阵列）的相位控制可以导致用于无线通信的纳米级定向发射器和接收器。
The spin torque(1,2) effect that occurs in nanometre-scale magnetic multilayer devices can be used to generate steady-state microwave signals in response to a d.c. electrical current(3-8). This establishes a new functionality for magneto-electronic structures that are more commonly used as magnetic field sensors and magnetic memory elements(9). The microwave power emitted from a single spin torque nano-oscillator (STNO) is at present typically less than 1 nW. To achieve a more useful power level ( on the order of microwatts), a device could consist of an array of phase coherent STNOs, in a manner analogous to arrays of Josephson junctions and larger semiconductor oscillators(10-12). Here we show that two STNOs in close proximity mutually phase-lock - that is, they synchronize, which is a general tendency of interacting nonlinear oscillator systems(13-15). The phase-locked state is distinct, characterized by a sudden narrowing of signal linewidth and an increase in power due to the coherence of the individual oscillators. Arrays of phase-locked STNOs could be used as nanometre-scale reference oscillators. Furthermore, phase control of array elements ( phased array) could lead to nanometre-scale directional transmitters and receivers for wireless communications.