Abstract
The coupling of spin-orbit materials to high energy barrier ($\sim$40-60 $k_BT$) nano-magnets has attracted growing interest for exciting new physics and various spintronic applications. We predict that a coupling between the spin-momentum locking (SML) observed in spin-orbit materials and low-energy barrier magnets (LBM) should exhibit a unique multi-terminal rectification for arbitrarily small amplitude channel currents. The basic idea is to measure the charge current induced spin accumulation in the SML channel in the form of a magnetization dependent voltage using an LBM, either with an in-plane or perpendicular anisotropy (IMA or PMA). The LBM feels an instantaneous spin-orbit torque due to the accumulated spins in the channel which causes the average magnetization to follow the current, leading to the non-linear rectification. We discuss the frequency band of this multi-terminal rectification which can be understood in terms of the angular momentum conservation in the LBM. For a fixed spin-current from the SML channel, the frequency band is same for LBMs with IMA and PMA, as long as they have the same total magnetic moment in a given volume. The proposed all-metallic structure could find application as highly sensitive passive rf detectors and as energy harvesters from weak ambient sources where standard technologies may not operate.
Highlights
The interplay between spin-orbit materials and nanomagnetism has attracted much attention due to interesting phenomena, e.g., spin-orbit torque switching [1,2], probing of the spin-momentum locking [3,4,5,6,7,8], spin amplification [9], the spin battery [10], and skyrmion dynamics [11,12], among other examples
We argue, using detailed simulation results, that such bandwidth arises due to the principles of angular-momentum conservation between the spins injected from the spin-momentum locking (SML) channel and the spins absorbed by the low-energy-barrier magnets (LBMs)
The frequency bandwidth of the multiterminal rectification is limited by a characteristic frequency fc that is determined by the angular-momentum conservation between the spins injected from the SML channel and the spins absorbed by the LBM
Summary
The interplay between spin-orbit materials and nanomagnetism has attracted much attention due to interesting phenomena, e.g., spin-orbit torque switching [1,2], probing of the spin-momentum locking [3,4,5,6,7,8], spin amplification [9], the spin battery [10], and skyrmion dynamics [11,12], among other examples. We predict that the spin-momentum locking (SML) observed in spin-orbit materials when coupled to a nanomagnet with a low energy barrier will rectify the channel current in the form of a voltage in a multiterminal structure. In the present discussion, pinning for a IMA or a PMA magnet occurs along the easy axis or the hard axis, respectively We argue that such wide-band rectification in an allmetallic structure [Fig. 1(a)] could be used for “passive” radio-frequency (rf) detection.
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