Jué Emilie, Rippard William H, Pufall Matthew R
Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
J Appl Phys. 2018;124(4). doi: 10.1063/1.5042092.
We have studied magnetization dynamics in three-terminal spin-torque oscillators (STOs) and present a direct method to compare the efficiencies of exciting oscillations in STOs through two mechanisms of spin transfer torque: the spin filtering torque (SFT) and the spin-orbit torque (SOT). The devices are composed of spin-valves patterned on a Pt wire that can be excited by a SFT and/or a SOT, depending on the pathway of the DC current. By varying the device and wire size, we tune and compare the efficiencies of both mechanisms in terms of current and current density. To a first approximation, for sufficiently narrow Pt wires (compared to the dimension of the spin-valve), significantly more current is required to excite the devices with SFT than with SOT, whereas in terms of current density, the SFT is up to three times more efficient than the SOT in the system studied. We investigate the limits of this comparison using control samples where the spin-valve is replaced by a magnetic tunnel junction (MTJ) or where the Pt wire is replaced by a Cu wire. A three terminal STO made with a MTJ is the most appropriate device to compare the efficiencies of both spin transfer mechanisms in order to avoid additional spin transfer torque induced by current shunted through the magnetic pillar.
我们研究了三端自旋扭矩振荡器（STO）中的磁化动力学，并提出了一种直接方法，通过自旋转移扭矩的两种机制来比较STO中激发振荡的效率：自旋过滤扭矩（SFT）和自旋轨道扭矩（SOT）。这些器件由在铂丝上图案化的自旋阀组成，根据直流电流的路径，可由SFT和/或SOT激发。通过改变器件和导线尺寸，我们从电流和电流密度方面调整并比较了这两种机制的效率。初步近似来看，对于足够窄的铂丝（与自旋阀尺寸相比），用SFT激发器件所需的电流比用SOT激发时显著更多，而从电流密度方面来看，在所研究的系统中SFT的效率比SOT高出三倍。我们使用控制样本研究了这种比较的局限性，其中自旋阀被磁性隧道结（MTJ）取代，或者铂丝被铜线取代。用MTJ制作的三端STO是比较两种自旋转移机制效率的最合适器件，以避免因电流分流通过磁柱而产生额外的自旋转移扭矩。
