[Todos] Coloquio Extraordinario, Departamento de Física, miercoles 13/7, 14hs

[pdmitruk en df.uba.ar]

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                                    COLOQUIO EXTRAORDINARIO
                                DEPARTAMENTO DE FÍSICA FCEyN - UBA

                                   http://coloquios.df.uba.ar/

                                    Charla, café y galletitas
                            En el Aula Federman, 1er piso, Pabellón I,
                                      Ciudad Universitaria


                                    Miercoles 13 de julio, 14hs,


                          Pure Spin Currents: Discharging Spintronics


                                          Axel Hoffmann


                                   Materials Science Division
                                   Argonne National Laboratory
                                         Illinois, USA



As semiconducting electronic devices are miniaturized to ever-smaller  
dimensions, power dissipation becomes an ever-increasing problem due  
to leakage charge currents. Spintronics may help addressing some of  
these issues by utilizing besides the charge degree of freedom also  
the electron spin. Conventional spintronics approaches are used for  
non-volatile devices, such as magnetic random access memory, where  
spin currents are mainly considered as spin-polarized charge currents  
and as a result the spin and charge currents are in parallel and  
directly coupled. Looking further into the future, the question  
arises, whether eliminating charge currents altogether could provide  
additional benefits for applications. Towards addressing this  
question, non-local device geometries allow for separating spin and  
charge currents, which in turn enables the investigation and use of  
pure spin currents [1]. This approach opens up new opportunities to  
study spin-dependent physics and gives rise to novel approaches for  
generating and controlling angular momentum flow. In this lecture, I  
will discuss different approaches for generating pure spin currents,  
such as non-local electrical injection from a ferromagnet,  
charge-to-spin current conversion via spin Hall effects, and spin  
pumping from ferromagnetic resonance. Furthermore, I will show how  
spin currents can then be used for gaining new insights into spin  
dependent phenomena. In particular, the temperature dependence of spin  
and charge relaxation times allows to identify different spin  
relaxation mechanisms [2]. In addition, spin pumping facilitates the  
generation of macroscopically large pure spin currents. This permits  
to quantify spin Hall effects with great precision, even in materials  
where these effects are relatively weak [3,4]. Finally, I will  
conclude with a brief outlook on the current scientific and future  
technological opportunities for pure spin currents.
This work was supported by the U.S. Department of Energy, Office of  
Science, Basic Energy Sciences, under contract No. DE-AC02-06CH11357.
[1] A. Hoffmann, Phys. Stat. Sol. (c) 4, 4236 (2007).
[2] G. Mihajlovi , J. E. Pearson, S. D. Bader, and A. Hoffmann, Phys.  
Rev. Lett. 104, 237202 (2010).
[3] O. Mosendz, J. E. Pearson, F. Y. Fradin, G. E. W. Bauer, S. D.  
Bader, and A. Hoffmann, Phys. Rev. Lett. 104, 046601 (2010).
[4] O. Mosendz, V. Vlaminck, J. E. Pearson, F. Y. Fradin, G. E. W.  
Bauer, S. D. Bader, and A. Hoffmann, Phys. Rev. B 82, 214403 (2010).