Deterministic current-induced spin-orbit torque (SOT) switching of magnetization in a heavy transition metal/ferromagnetic metal/oxide magnetic heterostructure with the ferromagnetic layer being perpendicularly-magnetized typically requires an externally-applied in-plane field to break the switching symmetry. We show that by inserting an in-plane magnetized ferromagnetic layer CoFeB underneath the conventional W/CoFeB/MgO SOT heterostructure, deterministic SOT switching of the perpendicularly-magnetized top CoFeB layer can be realized without the need of in-plane bias field. Kerr imaging study further unveils that the observed switching is mainly dominated by domain nucleation and domain wall motion, which might limit the potentiality of using this type of multilayer stack design for nanoscale SOT-MRAM application. Comparison of the experimental switching behavior with micromagnetic simulations reveals that the deterministic switching in our devices cannot be explained by the stray field contribution of the in-plane magnetized layer, and the roughness-caused Néel coupling effect might play a more important role in achieving the observed field-free deterministic switching. *

It has been shown that W in its resistive form possesses the largest spin-Hall ratio among all heavy transition metals, which makes it a good candidate for generating efficient dampinglike spin-orbit torque (DL-SOT) acting upon adjacent ferromagnetic or ferrimagnetic (FM) layer. Here we provide a systematic study on the spin transport properties of W/FM magnetic heterostructures with the FM layer being ferromagnetic Co 20 Fe 60 B 20 or ferrimagnetic Co 63 Tb 37 with perpendicular magnetic anisotropy. The DL-SOT efficiency DL ξ , which is characterized by a current-induced hysteresis loop shift method, is found to be correlated to the microstructure of W buffer layer in both W/Co 20 Fe 60 B 20 and W/Co 63 Tb 37 systems. Maximum values of 0.144 DL ξ ≈ and 0.116 DL ξ ≈ are achieved when the W layer is partially amorphous in the W/Co 20 Fe 60 B 20 and W/Co 63 Tb 37 heterostructures, respectively. Our results suggest that the spin Hall effect from resistive phase of W can be utilized to effectively control both ferromagnetic and ferrimagnetic layers through a DL-SOT mechanism. † / 2 s S He J e T J θ = h , where TM SH θ is the internal spin Hall ratio of the TM layer and TM e J represents the longitudinal charge current density flowing in the TM layer. TM/FM int T represents the spin transparency at the TM/FM interface [12,13] (note that TM/FM int 1 T = for a perfect transmission), which is related to the spin-mixing conductance [14,15]. The transmitted spin angular momentum from s J can be transferred to the magnetic moments in FM through a spin-transfer torque mechanism [16]. The final effect is therefore a dampinglike spin-orbit torque (DL-SOT) acting upon the FM layer, and the DL-SOT efficiency of a TM/FM bilayer heterostructure can be expressed as

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The purpose of this paper is to present a systematic analysis methodology for a newly taped-out High Voltage (HV) product that has encountered a 0% yield issue. In order to identify the root cause and improve the yield, a series of electrical analysis experiments designed to reveal the failure phenomenon of the charge-pumping circuit were applied. Combining spice simulation data, I-V curve measurements, CAFM measurements and nano probing, the difference in resistance for a multi-fingered symmetric device was revealed. A deductive method was then used to conduct layout analysis, and an in-line split experiment was developed to explain the failure phenomenon experienced by the multi-fingered HV symmetric device for a charge-pumping circuit.