Study On Fabrication And Properties Of Flexible Spintronic Devices

Flexible spintronic devices combine the advantages of flexible electronics and spintronics.Not only do they have the characteristics of being flexible and portable,but also have the advantages of low power consumption and high efficiency,which is very suitable for the application of wearable devices,Internet of Things,and medical fields.At present,the researches of flexible spintronic devices have just started in the world,and most of them focus on the selection of materials,optimization of devices,and fabrication processes.In this dissertation,two kinds of flexible spintronic devices were fabricated by indirect method and direct method respectively,and their properties were studied.The main contents of this thesis are as follows:(1)Fabrication and properties of the flexible magnetic tunnel junctions were investigated.Nanoscale magnetic tunnel junctions were fabricated on a rigid silicon substrate,and then transferred to a flexible substrate to realize the fabrication of nanoscale flexible magnetic tunnel junctions.The devices showed excellent performance: i)The devices with different size exhibited high magnetoresistance ratio(>120%);ii)TMR,high and low resistance of the devices are almost unchanged under different tensile strain,which is of great significance for flexible magnetic memory chips;iii)the resistance of the devices showed strain dependence in the weak magnetic field with change rate up to 13.6%,showing great potential in the application of highly sensitive strain sensing.Besides,in terms of microwave response,the devices displayed two resonant modes.The resonance frequency reached 5.78 GHz when magnetic field is +300 Oe;The weak changes of the effective demagnetizing field is generated by the effect of the magnetoelastic effect,while the resonance frequency and rectified voltage remain almost unchanged under different tensile strain.The study on the spin-torque diodes effect in the flexible magnetic tunnel junctions is expected to open up the application of flexible electronics in the detection of low-power microwave signals and microwave energy harvesting.(2)Research on flexible FeGa strip devices.FeGa films were deposited on flexible substrate directly using magnetron sputtering technology,and the flexible FeGa strip devices were prepared by micro-nano fabrication technologies.It is found that the FeGa films deposited on the flexible substrate are similar to those on the Si substrate,both of which have the A2 phase.And obvious anisotropic magnetoresistance effect was observed in the FeGa strip(AMR = 0.12%).In addition,the magnetoresistance ratio of the flexible device does not show obvious size dependence,indicating that the anisotropic magnetoresistance was mainly originated from the magneto-crystalline anisotropy.