Manipulation Of Magnetoelectric Transport Properties By Ion Migration Driven By Electric Field In Co/Pt Heterojunctions

The advent of the era of big data has put forward more stringent requirements for the efficiency of data storage.The first generation of magnetic random-access memory(MRAM)is driven by the magnetic field,the second generation of MRAM is driven by spin transfer torque(STT).So far,the MRAM has been developed into the third generation that magnetization switching driven by spin-orbit torque(SOT).The continuous discovery of various torque effects driving the magnetization switching has led to the generation-bygeneration development of MRAM.The SOT can quickly switch FM’s magnetization direction or drive the magnetic domain wall(DW)and skyrmion’s motion,providing a low energy consumption,high speed,and high-efficiency method for regulating the magnetic state of ferromagnetic thin films.However,the SOT efficiency needs to be improved to realize the practical application of SOT-based MRAM,and the in-plane assistant magnetic field required to drive the magnetization switching is also a major application obstacle.The electric field is regarded as an excellent means to control the properties of magnetoelectric transport due to its non-volatility,reversibility and low energy consumption,which provides a way for the regulation of SOT.The electric field control of SOT not only has many advantages but also can be developed into a programmable logic operation,which has important physical significance and potential application prospects.Focusing on the manipulation of SOT,the realization of field-free magnetization switching and the application of SOT devices in memory and computing integration,we explore the manipulation of electric fields on relevant magnetoelectric transport properties in metal heterojunctions.The main research contents and results are as follows:(1)In TaN/Co/Pt/TaN heterojunction films,possessing in-plane magnetic anisotropy,we use H2O-doped ionic liquid gating to realize the reversible and non-volatile manipulation of the spin Hall effect of Pt.And the spin Hall angle can be modulated by 48%within an accessible gate voltage range.The increase in the spin Hall angle is demonstrated to be caused by the adsorption of hydrogen ions on the Pt surface and the consequent enhancement of the spin Hall conductivity under positive voltage.The decrease in the spin Hall angle is caused by the desorption of hydrogen ions on the Pt surface.Furthermore,the enhancement of the spin Hall angle is beneficial to reduce the critical current density for driving the domain wall motion.These results supply a method for the dynamic control of the charge-to-spin current conversion,which will promote the development of spintronic devices driven by electric fields.(2)Magnetized films with perpendicular magnetic anisotropy have higher storage density than in-plane magnetic anisotropy.Therefore,the SOT efficiency is manipulated in the system with perpendicular magnetic anisotropy.In two TaN/W/Pt/Co/Pt/TaN heterostructures dominated by opposite spin polarization directions,the reversible and non-volatile control of the critical current for magnetization switching and spin Hall efficiency is achieved by using ionic liquid gating-induced hydrogen ion adsorption and desorption in the upper Pt layer.The reversible control of the critical current provides support for the reduction of energy consumption and the application of SOT MRAM devices.The magnetization switching with PMA requires an in-plane assistant magnetic field to break the mirror symmetry,which is thought to be a major obstacle to the application of SOT devices.The thinning of the Pt and TaN capping layers activated the oxygen ion migration toward the Co layer under IL gating,resulting in an exchange bias field and allowing field-free magnetization switching.These results offer an intriguing opportunity to promote the development of SOT-based spintronic devices from the perspective of iontronics with low energy dissipation.(3)The von Neumann architecture separated the memory from the computer,which paved the way for a huge increase in computer speed,but also made the bandwidth of data transfer between the central processor and the memory a bottleneck.The integration of storage and computing provides a way to solve the bottleneck of von Neumann architecture.The realization of field-free magnetization switching under the control of oxygen ion migration driven by electric field is accompanied by the change of switching polarity.The switching polarity changes from clockwise with the positive assistant field in the pristine state to anti-clockwise,which lays the foundation for the implementation of Boolean logic operations.16 Boolean logic functions could be realized through the combined control of gate voltage and the pulse current.This study explores the electric field control of programmable spin logic devices.