Spin dynamics in magnetic nanostructures

点击翻译按钮获取中文摘要

Summary The spin of the electron rather than its charge has created remarkable opportunities in electronics, coined spintronics. The rapid progress in this field requires further advances in understanding of spin interactions in nanoscopic geometries. Our studies involve spin dynamics with emphasis on the study of pure spin currents unaccompanied by a net electric charge. a) We are going to continue to study the spin current transport in non-magnetic metallic layers which serve in spintronics, as interconnects between the magnetic source and sink terminals. Particular emphases will be put on heavy metallic thin films which have a large spin orbit interaction, electron spin correlations, and high resistivity with the spatial electron localization. Heavy metal Pt, Ta, and W metallic films are very attractive in spintronics. They have very large Spin Hall Effect (SHE) and interface Spin Orbit Torque (SOT), allowing one to operate Magnetic Random Access Memory (MRAM) by using an electric current in heavy metals. After firmly establishing the spin transport parameters in Pt, Ta, and W, we will study the reflection of spin current at the Au/(Pt,Ta,W) interfaces. We expect, based on our PRL 2013, to observe quantum well states in Fe/Au/Pd,Pt,Ta,W heterostructures due to spatial confinement of spin current in the Au layer. This is fundamental physics because quantum well states are typical to reversible processes while spin pumping is an irreversible process. Heavy metals will be used also in spin torque driven nanopillar devices with the intention to further understand the role of interface SOT and spin loss memory, allowing one to improve Magnetic Random Access Memory (MRAM) architecture. b)Large spin currents can be achieved by using a large angle of precession of the magnetic moment at the ferromagnet/normal metal interface. In fact, this can lead to a comparable spin current using a spin polarized net charge current in spin torque devices. Yttrium Iron Garnet (YIG) films have become one of the most studied materials for generating pure spin currents. We are going to construct a device that is based on YIG/Au/Py(Permaloy) structure, where Py is used as a spin current detector. The development of efficient and quantitative spin current detectors is an important part of spintronic technology. c)We will collaborate with Prof. E. Girt's group in the development of magnetic superlattices with high perpendicular magnetic anisotropy (PMA) for applications directed to high density magnetic memory media and MRAM. With the new clean room facility in SFU's 4D LABS, we can fabricate nanosize pillar structures which can be driven either by spin polarized current or SHE and SOT. Our unique experimental research enables us to carry out a broad program advancing both the engineering and basic science progress in the development of materials and systems based on spin pumping, spin current transport and spin torque mechanism.