高磁电阻磁性隧道结的几种微制备方法研究

利用金属掩模法优化了制备磁性隧道结的实验和工艺条件，金属掩模的狭缝宽度为100 μm. 采用4 nm厚的Co₇₅Fe₂₅为铁磁电极和10或08 nm厚的铝氧化物 为势垒膜， 直接制备出了室温隧穿磁电阻（TMR）为30%—48％的磁性隧道结，其结构为Ta(5 nm)/Cu(25 nm)/Ni₇₉Fe₂₁(5 nm)/Ir₂₂Mn₇₈(10 nm)/ Co₇₅Fe₂₅ (4 nm)/Al(08 nm)-O/Co₇₅Fe₂₅(4 nm)/Ni₇₉Fe ₂₁(20 nm)/Ta(5 nm).同时，利用刻槽打孔法和去胶掀离法两种光刻技术并结合Ar离子束刻蚀及化学反应刻 蚀，制备出面积在4 μm×8 μm—20 μm×40 μm、具有室温高TMR和低电阻的高质量磁性 隧道结.300 ℃ 退火前后其室温TMR可分别达到22% 和50%.研究结果表明，采用光刻中的刻 槽打孔或去胶掀离工艺方法制备的小尺寸磁性隧道结，可用于研制磁动态随机存储器和磁读 出头及其他传感器件的磁敏单元. 关键词： 磁性隧道结 隧穿磁电阻 金属掩模法 光刻法     

Vortex domain structures and dc currentdependence of magneto-resistances in magnetic tunnel junctions

Microfabrication and the magneto-transport characteristics of the magnetic tunnel junctions (MTJs) with a spin-valve-type structure of Ta (5nm)/Ni_{79}Fe_{21} (25nm)/Ir_{22}Mn_{78} (12nm)/Co_{75}Fe_{25} (4nm)/Al(0.8nm) oxide/Co_{75}Fe_{25} (4nm)/Ni_{79}Fe_{21} (20nm)/Ta(5nm) were investigated in this paper. A series of experimental data measured with a MTJ was used to verify a magnon-assisted tunnelling model and theory. Furthermore, a micromagnetics simulation shows that the butterfly-like vortex domain structures can be formed under a current-induced Oersted field, which decreases the net magnetization values of the ferromagnetic electrodes under a large dc current (i.e., in high voltage regimes). It is one of the main reasons for the tunnel magnetoresistance ratios to decrease significantly at high voltage biasing.