Tuning Spin-related Magnetic And Transport Of Multilayer Films With Interface Modification

Accompanying the electronic integrated functional devices going to 10 nanometers scale,the contradiction between the energy loss and the integration density has become more serious.The electron spin has low operation energy,high speed and quantum properties,which provides us with an unprecedented chance to explore the future of information revolution.The manipulation of the spin dynamics and spin current transport are of fundamental interest and are essential for realizing full-spin-current based spintronics functional devices and spin microwave devices.The interface effects has attracted much interest due to its impact on the spin dynamics and spin current transport of spintronic devices,such as electric injection across ferromagnetic/semiconductor(FM/SC)interfaces and the spin Hall effect(SHE)in normal metal/ferromagnetic(NM/FM)heterostructures.The present thesis is concerned with the role of the interface in spin dynamics and spin current transport properties of magnetic/nonmagnetic heterostructures.Firstly,the spin and orbital magnetic moments of the ZnxFe3-xO4/Si thin films have been obtained.Both the magnetization dynamics and transport properties of ZnxFe3-xO4/Si thin films were systematically investigated.Secondly,by employing Tb interlayer or introducing Tb impurities in Py to tune the Py/Pt interface,the spin-orbit torque of the thin films were studied by using planar Hall effect(PHE)measurements.Finally,we investigated the effect of interface of the CoFeB/NM bilayers and CoFeB/NM/CoFeB sandwich structures on magnetization dynamics.The main results of research work is as follows:1.Ion doping offers tunable magnetic and electrical properties in Fe3O4 thin films without changing the half metallic properties,which helps to obtain more matched contact conductivity between Fe3O4 and semiconductors.This avoids the boundary spin scatting due to an insulator inset with the tunnel barrier between the two materials.In our work,ZnxFe3-xO4 thin films on Si substrates with dilute Zn substitution were fabricated.Based on the structure of(111)-textured in ZnxFe3-xO4 films,a(111)-texture magnetic anisotropy expression is proposed.By fitting the FMR resonance field,the value of texture anisotropies in the films quantitatively determined.By useing XMCD the electronic structure and magnetic moments at different Fe ionic sites in our ZnxFe3-xO4 thin films are obtained.Through these measurements,we have revealed the tunable magnetic moment in ferrimagnetic oxide ZnxFe3-xO4 thin films by controlling the doping level of nonmagnetic Zn.This result is consistent with the conclusion of out-of-plane angular dependence of FMR linewindth,in which the Gilbert damping coefficient increases with increasing Zn substitution.In addition,the transport properties across the ZnxFe3-xO4/Si heterostructures exhibits a clear asymmetry on ?-? curves,indicating the presence of the Schottky barrier.The fitting of the ?-? curves of ZnxFe3-xO4/Si interface demonstrates that the height of the Schottky barrier increases with increasing doping-level,which recommends ZnxFe3-xO4 as a potential material for spintronic applications.2.Along with gradual penetrating to the spin-orbit interaction in spintronics,the spin-orbital effective torque has attracted great attention because of its high efficiency in manipulate spin dynamics.We adopted a novel second-order PHE method to study the effect of Tb inseted layer on current induced spin-orbit torque of Py/Tb(d)/Pt thin films.The spin-orbit filed of Py/Tb(d)/Pt thin films,measured by PHE from Hall Bar,decreases with increasing thickness of Tb interface layer,indicating the spin-orbit torque of the Py/Pt thin films due to spin current of Pt layer decreases with the introduction of Tb interface.Furthermore,we provide an efficient way for tuning the Py/Pt interface though Tb doping in Py layer,and the spin-orbital field shows an increase in TbxPy1-x/Pt compared with that of the Py/Pt thin film.Our work suggests that there may be additional opportunities for enhancement the strength of spin orbit torque through further optimized modification of FM/HM interfaces,which also help the rare earth element for developing spin-orbit interaction-driven devices.3.The spin pumping effect in magnetic/non-magnetic heterostructure is a non-localized processes,and such non-local spin dynamics manifests as an additional spin damping,governed by the intrinsic properties of magnetic layer and non-magnetic layer,as well as interface between them.We present a study of the magnetization dynamic properties on the CoFeB/NM(Pt,W,Ta and Cu)systems,and the relationships between the enhanced damping and the thickness of non-magnetic layer are revealed.In particular,we quantitatively determined the spin diffusion length of Pt,W,Ta and Cu,as well as the spin mixing conductance between these non-magnetic metal and CoFeB thin films interface.In addition,the magnetization dynamics of the collinear CoFeB/NM/CoFeB sandwich structures are also investigated by the spin pumping theory and the long-range dynamic exchange coupling model.It was found that the collinear CoFeB/NM/CoFeB structures present an enhancement of effective spin diffusion length by the addition of the NM/CoFeB interlayer,which may be helpful to reveal the role of interface in CoFeB/heavy metal heterostructures.