Preparation And Characteristics Of The Magnetic Multilayer Film Of Antiferromagnetic Pinning Material Layer

Spintronics is an emerging discipline developed in the last century.Since the discovery of the tunnel magnetoresistance effect,the magnetic random access memory(MRAM)with a magnetic tunnel junction(MTJ)as the core structure has attracted people's attention,because it has good non-volatility and is considered a perfect replacement for traditional memory Product.At the antiferromagnetic layer/ferromagnetic layer interface of the magnetic tunnel junction,due to the exchange bias,the antiferromagnetic substance can pin the ferromagnetic substance,which is the most critical step for the successful fabrication of the magnetic tunnel junction.In this thesis,the physical theories of magnetoresistance effect and exchange bias effect are explained.Magnetic multilayer films with iron-manganese alloy and iridium-manganese alloy as pinned layers are prepared,and their magnetic properties are explored.The results are as follows:(1)Preparation and characteristics of magnetic multilayer film samples with Fe Mn as the pinned layerThe film samples with stacking structure of SiO₂/Ta/Ni₈₁Fe₁₉/Fe₅₀Mn₅₀/Ta were prepared using RF high vacuum magnetron sputtering apparatus.By testing the magnetic properties of the film,(a)explored the relationship between the exchange bias effect at the antiferromagnetic layer/ferromagnetic layer interface and the thickness of the antiferromagnetic layer.When the thickness of the ferromanganese layer is above its critical thickness,The film has pinning properties,that is,there is an exchange bias effect at the antiferromagnetic layer/ferromagnetic layer interface;and above the critical thickness of the antiferromagnetic layer,the exchange bias field of the film does not gradually increase with its thickness.If it becomes larger,this change is oscillating,that is,there is a specific thickness that can produce the maximum value of the exchange bias field(12nm);(b)The influence of the heat treatment temperature on the film exchange bias field during the preparation of thin film samples was explored.As the heat treatment temperature gradually increased,the exchange bias field and coercivity of the thin film samples gradually decreased;when the heat treatment temperature gradually increase.When rising to the blocking temperature of the antiferromagnetic material,the anisotropy of the antiferromagnetic particles decreases,and the temperature rises,the spin arrangement of the antiferromagnetic particles is disordered,and the antiferromagnetic layer does not affect the spin orientation of the ferromagnetic layer;(c)The effect of the cooling field on the exchange bias field of the film is explored.The cooling process in the magnetic field is that the direction of the ferromagnetic layer magnetization determines the direction of the exchange bias,not the direction of the cooling field.For most antiferromagnetic/ferromagnetic double-layer film,when the ferromagnetic layer is saturated in the cooling field,the cooling field has little or no effect on the exchange bias.(2)Thermal stability of magnetic multilayer film with Ir Mn pinned layerThestackingstructureof Ta(10nm)/Ni Fe(5nm)/CoFe(3nm)/Al₂O₃(1.8nm)/CoFe(3nm)/Ir Mn(10nm)/Ni Fe(2nm)/Ta(5nm)/SiO₂/Si were prepared using RF high vacuum magnetron sputtering apparatus.Evaluate how the magnetic properties change by performing thermal processing in the presence or absence of an external magnetic field,(a)It was found that in the absence of a magnetic field,the magnetic properties of the film deteriorated after thermal processing at 300°C or higher.A simple model was established to explain the reason for the change in magnetic properties.In the case of a magnetic field,the direction of the spin of the pinned layer is dispersed by performing thermal processing,which degrades the magnetic properties of the film;(b)A method to restore the magnetic properties of the film sample to its original state after the change is proposed,that is,the magnetic properties of the MTJ multilayer film can be passed at 300?-365?after thermal processing without a magnetic field.It was recovered by performing thermal processing in a magnetic field of 18k Gs at 300?,and it was verified through experiments.