| At present,the internet of everything and digitalization has become the future development trend.This requires optimization and innovation of information storage technology.Magnetic memory,which uses spin-orbit torque to realize information reading and writing,has received the most extensive attention from scientists due to its high storage density,low energy consumption,good storage stability,and non-volatility of information.It is also regarded as a new generation of data storage with the most development and application potential.For the magnetic memory that uses the spin-orbit torque to realize the storage function,the writing of information is realized by the switch to the magnetization.The spin-orbit torque that drives the magnetization to switch usually originates from the spin current generated by the spin Hall effect(SHE)in the heavy metal body or the Rashba effect at the interface.Therefore,how to improve the conversion efficiency of charge current to spin current has become one of the main points of attention to researchers.The exchange bias effect generated by the interface exchange coupling also plays an important role in the new generation of magnetic memory,but there are still many problems related to the exchange bias effect involving the interface interaction,which need further research.In addition,the researchers also found that the spin-orbit torque can not only realize the switch to the ferromagnetic magnetic moment but also control the antiferromagnetic interface magnetic moment.This suggests that current-controlled remanent state Hall resistance-based multi-state storage may be realized in a double-exchange biased regime with a single remanence state through spin-orbit torque.Focusing on the above-mentioned problems,in this paper,Co-based ferromagnetic and antiferromagnetic samples were prepared by magnetron sputtering technology,respectively.Using an electrical transport measurement platform,magneto-optical Kerr microscope,atomic force microscope,and other instruments,the structure,magnetic properties,and the electrical transport properties were researched,and the results acquired are as follows:(1)Using magnetron sputtering technology,prepared Pt/Co/Pt samples,and by changing the degree of interfacial oxidation of the Co layer between Co and the upper layer of Pt,the effects of interfacial oxidation on the perpendicular magnetic anisotropy(PMA)and spin-orbit torque(SOT)of magnetic heterojunctions were systematically investigated.Experimental results show that the interfacial oxidative modification significantly affects the perpendicular magnetic anisotropy and magnetic domain structure of the samples.The appearance of the oxide intercalation layer blocks the formation of the Co/Pt interface,thereby reducing the perpendicular magnetic anisotropy of the sample and affecting the magnetic domain structure of its switch process.Under the experimental conditions of this research team,the Co layer will form an oxide layer with a thickness of about 0.4 nm after 30 minutes of natural oxidation.The oxidation operation will reduce the effective field of the perpendicular magnetic anisotropy of the samples from 9565 Oe to 5263 Oe by up to50%.Meanwhile,a current-driven magnetization switch was observed in Pt/Co/Pt and Pt/Co/Ta samples,while this switching process was not achieved in Pt/Co/CoO/Pt sample.In addition,this study also quantitatively measures the spin-orbit coupling effective field conversion efficiencies??DL and??FL of different samples using the method of frequency-doubling voltage test.Among them,the??DLand??FL of the Pt/Co/Ta sample of antisymmetric configuration are relatively large,which are 5.62±0.09 and 4.04±0.04 Oe/(10~6A/cm~2),respectively.The??FL of the more symmetrical Pt/Co/Pt and Pt/Co/CoO/Pt samples is significantly smaller than that of the Pt/Co/Ta sample,and the??DL of the Pt/Co/Pt sample is 3.6 times that of the Pt/Co/CoO/Pt sample.The experimental data confirm that the interface Rashba effect is significantly suppressed due to the symmetrical design of the structure,and the spin loss of the spin current at the interface is also significantly reduced due to the appearance of the oxide insertion layer.(2)Through magneto-optical Kerr microscopy,out-of-plane exchange bias and in-plane exchange bias were simultaneously observed in Pt/Co/IrMn/Co series samples with different ferromagnetic and antiferromagnetic layer thicknesses,and the hysteresis loops of the samples in the perpendicular direction to the film surface show the double-exchange bias phenomenon,which is related to the non-uniform stray field in the chamber during sample growth.By testing the hysteresis loops of the samples,it is found that the increase in the thickness of the ferromagnetic layer directly leads to the decrease of the exchange bias field.When the thickness changes more obviously,the exchange bias field and the reciprocal of the thickness of the ferromagnetic layer will be exhibiting a linear relationship that fits the theoretical model.At the same time,the thickness of the antiferromagnetic also affects the magnitude of the exchange bias field at room temperature:when the thickness of the antiferromagnetic layer is less than 4 nm,the too low antiferromagnetic Neel temperature results in no ferromagnetic and antiferromagnetic coupling at room temperature,and there is no exchange bias in the samples;When the ferromagnetic thickness is large,the interface exchange coupling constant does not change with the thickness of the antiferromagnetic,so the exchange bias field remains unchanged.These results suggest that the exchange bias originates from the interfacial exchange coupling effect between Co and IrMn.Subsequently,the current regulation of the remanent states of the double-exchange biased hysteresis loops in the out-of-plane direction was realized under three different external magnetic field configurations,which demonstrated that the current can be realized in a double-exchange-biased system with a single remanent state via the spin-orbit torque customized multi-state storage based on remanent state Hall resistance. |
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