Temperature dependence of Spin Pumping into a Topological Insulator
Faris Basheer Abdulahad1*, Wen-Kai Chiu1,2, Shang-Fan Lee1,2
1Institute of Physics, Academia Sinica, Taipei, Taiwan
2Graduate Institute of Applied Physics, National Chengchi University, Taipei, Taiwan
* presenting author:Faris Abdulahad, email:farissofya@gmail.com
The emerging field of spintronics has received an increasing interest during the past two decades due to its widespread applications.1-2 Spintronic, involves the detection and manipulation of electron spin, which is usually achieved by bringing a ferromagnet to a contact with a normal metal or a semiconductor. However, the spin relaxation due to the spin-orbit coupling in these materials can limits the spin life time.3 Recently, it was demonstrated that topological insulators (TI) can have a very strong spin-orbit coupling which makes them a promising candidates for spintronics.4-5 However, the field of TI’s spintronics is relatively new and still needs a lot of efforts to demonstrate its basics. Here we study the temperature dependence of spin pumping into the TI materials. The samples structure consist of a ferromagnet (FM) / TI heterostructure, in which, a 40 nm thick NiFe film was grown by sputtering on the top of Bi2Te3 layer with different thicknesses up to 100 nm. Under the resonance condition of the NiFe layer, a spin current is produced from the NiFe, emitted and accumulated at the adjacent TI layer, and then a voltage difference can be detected due to the Inverse-Spin-Hall effect (ISHE). The ferromagnetic resonance (FMR) spectrum recorded at all measuring temperatures can be used to estimate the effective magnetic field by fitting our experimental data to the well-known Kittel equation. The ISHE voltage signal measured at the resonance condition on the TI’s side shows strong dependence both on the temperature and the TI’s thickness. The behavior can be explained due to different surface and bulk contributions of the TI. More detailed results will be discussed during the meeting.

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Keywords: Ferromagnetic Resonance, Topological Insulator, spin pumping, Inverse-Spin-Hall effect, effective magnetic field