The Spin Pumping Effect Of Metallic Multiplayer Based On Near-field Microwave Probe

Nowadays,traditional charge-based semiconductor devices,which is easy to lose data and has low throughput performance,are facing great challenges.By contrast,the spin-based spintronics have attracted great attention for its advantage of low heat loss and high-speed data transfer.However,through there are theories like spin-orbit coupling which provide theoretical practicality for the injection of spin current,the highly efficient manipulation of spin current in actual spintronics still remain challenges.One of the main ideas to solve the problem is improving the generation efficiencies of spin current like using materials which have strong spin-charge conversion efficiency.The mainly used method of characterizing the spin-charge conversion efficiency is the spin pumping effect(SPE)of the ferromagnetic/nonmagnetic bilayer and the inverse spin Hall effect(ISHE)of the metal monolayer,specifically,the SPE will transfer polarized electron spins from the ferromagnet to the adjacent metal layer to inject the spin current,while the spin current will be converted to charge current due to the ISHE of the metal layer.Researchers has measured the spin-charge conversion efficiency of many metallic materials by this SP-ISHE method,such as Pt,Ta,Pb and so on,but the traditional SPE measurement system is only suitable for characterizing a single sample,not efficient in characterizing batch samples.For this purpose,we build a scanning spin pumping spectrometer using a shorted microwave probe in this thesis,which has the advantage of high-throughput characterization of a large number of samples.We deposited the Ta films with thickness gradient distribution on a same substrate by the inclined sputtering method and used the scanning system to characterize the spin transport characterization of Ta,the spin diffusion length and spin Hall angle of Ta is obtained as 4.2 nm and-0.014,respectively.Besides,we found that the voltage signal is sensitive to the variation of microwave magnetic field and there is linear corresponding relationship between them,thus,we can image the microwave magnetic field using the spin pumping effect of Py/Ta bilayer film,the mapping results are consistent with the simulation results,which demonstrates the effectiveness of this mapping method.