Investigation Of Materials Properties Based On The Spin-Scattering Related Effects

Spintronics focuses on the quantum degree of freedom(spin)of electrons and spin transport in condensed matter.The giant magnetoresistance effect discovered in 1988 is the beginning of the spintronics,which is attributed to the spin transport of electrons between Cr and Fe layers by M.N.Baibich.The integrated electronic devices based on giant magnetoresistance effect such as spin valves and magnetic tunnel junctions have been applied in nonvolatile magnetic memory,high-precision sensors and bio-sensors.Although spintronics has shown great potential in the field of electronic information,its application such as a general method of exploring the properties of materials is rarely involved.Therefore,the properties and structure of different materials were investigated by means of effects related to spin scattering in this study.The main contents and conclusions are as follows:(1)The origin of Invar effect was studied systematically utilizing anomalous Hall effect.Comparing with the anomalous Hall effect of pure Fe and Ni,it is found that the anomalous Hall resistivity of Invar alloy increases non-monotonously with temperature increasing.Not only the band-structure-originated intrinsic but also the external scattering related extrinsic anomalous Hall resistivities deviate from their original trend when the thermal expansion anomaly occurs,while there is no deviation in the anomalous Hall signal of pure Fe and Ni.The deviation can be attributed to the simultaneous change of intrinsic and extrinsic.Our results suggest that a structural change accompanying with forming and growing of nano-size domains should be more appropriate than a pure electron high spin-low spin transition proposed by Weiss for the explanation of the Invar effect,which can also be supported by the analysis of the normal Hall effect.(2)The inverse spin Hall effect related to spin scattering in conductive oxides was investigated.The bismuth oxide thin films with different thicknesses were prepared from a sintered oxide target by an rf-sputtering system.Then,permalloy/bismuth oxide bilayer spin pumping devices were developed,with which voltage signals corresponding to the inverse spin Hall effect were confirmed by the spin pumping technique.Furthermore,by systematic studying of bismuth-oxide thickness dependence of those spin Hall voltages,the spin Hall angle and spin diffusion length were quantitatively estimated.The spin Hall angle is 0.007 and the spin diffusion length is 6.5 nm.In this work,the origin of Invar effect and bismuth oxide with observable inverse spin Hall effect were studied systematically from the point of view of spin scattering.This work introduces the spintronics into materials.On the one hand,it expands the application of spintronics materials and proposes new methods of materials research.On the other hand,it provides the data support for the design and development of spin-based devices.