Spin–orbit magnetic state readout in scaled ferromagnetic/heavy metal nanostructures

Abstract

Efficient detection of the magnetic state at nanoscale dimensions is an important step to utilize spin logic devices for computing. Magnetoresistance effects have been hitherto used in magnetic state detection, but they suffer from energetically unfavorable scaling and do not generate an electromotive force that can be used to drive a circuit element for logic device applications. Here, we experimentally show that a favorable miniaturization law is possible via the use of spin-Hall detection of the in-plane magnetic state of a magnet. This scaling law allows us to obtain a giant signal by spin Hall effect in CoFe/Pt nanostructures and quantify an effective spin-to-charge conversion rate for the CoFe/Pt system. The spin-to-charge conversion can be described as a current source with an internal resistance, i.e., it generates an electromotive force that can be used to drive computing circuits. We predict that the spin-orbit detection of magnetic states can reach high efficiency at reduced dimensions, paving the way for scalable spin-orbit logic devices and memories.Modern computing transistor technology is scaled to tens of nanometers 1 in lateral dimensions driven by the favorable miniaturization (Moore's Law) 2 . Such a favorable miniaturization 3 is an essential requirement for enabling spin logic 4-7 in computing but it has so far been a missing focus in spintronics. In particular, energy efficient detection of the magnetic state at the nanoscale dimensions is an important step to realize spin logic devices for computing. Up to now, magnetic state sensing techniques have relied on magnetoresistances such as anisotropic magnetoresistance (AMR) 8 , giant magnetoresistance (GMR) 9,10 , colossal magnetoresistance (CMR) 11 , and tunneling magnetoresistance (TMR) 12 . Even if TMR has been steadily improved to large values (>1000%) 13 , the magnetoresistance techniques are unfavorable in terms of energy for sensing a magnetic state because the resistance of the device increases quadratically when scaling down the area of the device 14 . Also, importantly, magnetoresistance techniques cannot generate an electromotive force (i.e., an electric current) that can be used to drive another circuit element, a requirement for a

2D materials for spintronic devices

“…A new spin logic device concept was also proposed by combining the spin-orbit coupling (for reading) and the magnetoelectric effect (for writing), showing that this magnetoelectric spin-orbit logic exhibits superior energy efficiency than the CMOS technology (by a factor of 10 to 30) 195 . This may benefit greatly from the unique spin properties (large spin Hall angles, long spin lifetime) of 2D materials and their heterostructures 196 . Looking further into how 2D materials can better enable or advance these newer forms of the spin logic device will potentially pave the way for the postsilicon spintronics era.…”

Evidence of interfacial asymmetric spin scattering at ferromagnet-Pt interfaces

“…Although it is usually overlooked in spinorbitronics, it allows completing the spin transport picture, with a major role in our metallic FM/SOC nanostructures. Contrarily to what could be expected, resistive FM/Pt interfaces can favorably enhance the spin Hall signal, which is useful for the spin-orbit magnetic state readout 5,6 .…”

“…The efficiency of the charge to spin conversions is a crucial issue, as it determines how much torque that can be generated to write information by the spin-orbit torques (SOTs) 3,4 . It is also essential in the reciprocal mechanism, for example in the reading process 5 of magneto-electric spin-orbit logic devices 6 , a beyond-CMOS technology where a spin current emitted by a ferromagnetic (FM) element generates a transverse charge current, whose sign depends on the magnetic states. Beyond the conversion rate by the spin-orbit coupling (SOC), the interface is the other key element to be optimized.…”

“…Obtaining high values of direct SHE and inverse SHE signals are necessary, for instance for developing SO magnetic readout 5 . As the interface resistance is basically a resistance to the spin current injection, one can intuitively expect that the signals will decrease when increasing the interface resistance.…”

Stimuli‐Responsive Memristive Materials for Artificial Synapses and Neuromorphic Computing

“…Unlike conventional CMOS transistors, memristors represent an emerging class of bioinspired devices that directly simulate synaptic and neural functions. [ 13–16 ] Memristors can be analog and nonvolatile, integrating memory and logic units in one nanoscale device. For memristive materials, tunable and continuous resistance states or optical properties can be induced by an external stimulus (e.g., an electric, magnetic or optical field), and information can be stored as different states.…”