Implementation Of Multi-bit Magnetic Storage Cell Based On SOT Effect

To overcome memory wall of the von Neumann bottleneck,researchers have proposed a storagecomputing fusion architecture that integrates storage and computing units.The commonly used storage media in storage-computing fusion architecture,such as static random access memory(SRAM)and dynamic random access memory(DRAM),are volatile and have limited application scenarios.Flash memory,which is non-volatile,has a short lifespan,requires error-correction mechanisms,and can only be read and written a limited number of times.Therefore,based on spinelectronic devices,researchers have conducted research on magnetic storage units using Hall-bars,which have long lifespans,are easy to fabricate,have continuously variable resistance states,nonvolatile programming,and support in-memory computing,and have certain advantages in achieving multi-bit storage.Therefore,in this paper,the following research is conducted around how to implement multi-bit information storage cells based on SOT’s Hall-bar devices:(1)Hall-bar performance testing and model building.Based on the spin-orbit torque theory,the optimal structure of the device was designed to achieve zero-field spin-orbit torque flipping.The device’s magnetic hysteresis loop,equal and unequal pulse current-driven magnetization reversal curves were measured using an electrical testing platform.The best values for the pulse amplitude,width,and number of pulses for device state adjustment were obtained,and a Hall-bar electrical model based on the number and width of pulse currents was established using Verilog-A language.The accuracy of the electrical model was verified by simulating the read and write circuits.(2)Design and implementation of consistency compensation scheme.In response to variations among different devices,a bias compensation method and circuit based on Hall-bars were proposed for the first time.The bias circuit was connected to the Hall-bar readout path in a cascade form with a bias resistor,achieving read-write separation and compensating for the bias error of a single Hallbar,thus reducing the impact of device variation problems.Experiments show that the Hall-bar bias is reduced from greater than 180 mV to 0.443 mV using this method,which effectively solves the device output bias consistency problem.(3)Hall-bar magnetic storage unit circuit simulation,implementation,and testing.The magnetic storage module and its peripheral circuits were designed and simulated using the Hall-bar electrical model to verify the feasibility of the entire system.Based on the characteristics of Hall-bar,such as multi-state storage,a pulse current amplitude,width,and number state-adjustment method was used to construct a Hall-bar-based magnetic storage module for the first time,enabling precise control and programming of the Hall-bar.A test platform was set up to measure the repetition testing curve of the Hall-bar anomalous Hall resistance as the pulse current amplitude,width,and number changed and the output of a single Hall-bar at different reading signals.In this paper,two devices,CoPt single-layer and multilayer thin film,are studied and tested by magnetic storage module.The experimental results show that the module can achieve repeatable state storage of not less than 3 bits,can support analog multiplication operation of read current and multibit anomalous Hall resistance,and the actual test results of multiplication operation have an error of not more than 5.4% with the theoretical value,and a single device can measure up to more than The actual test results of the multiplication operation have an error of more than 5.4% with respect to the theoretical value,and a single device can measure up to more than 50 resistance states.The Hall-barbased magnetic storage cell enriches the variety of storage cell circuits and provides a new way to implement the storage and computing integration.