TOPIC Nano-Spintronic Devices 
AREA Microelectronic Technologies & Devices  
SPEAKER Professor Atsufumi Hirohata, Department of Electronics, University of York 
DATE 30 June 2015, Tuesday 
TIME 11:00 am to 12:00 pm 
VENUE Seminar room E1-06-04, Engineering blk E1, Faculty of Engineering, NUS 
FEES No Charge 

Recent advancement in nanofabrication and growth allows the utilisation of spin-polarised electrons in transport and dynamics, resulting in the development of spintronic devices [1]. In the spintronic devices, the key technologies are injection, manipulation and detection of spin-polarised electron in a non-magnetic media with high efficiency.Conventionally such a spin-polarised electron current has been injected into a non-magnetic material by flowing an electrical current through a ferromagnetic layer. However, its spin polarisation is dependent upon the interfacial properties, such as conductance matching, junction resistance and interfacial resonant states. We recently succeeded to fabricate an abrupt Fe/GaAs(001) interface for the first time and have demonstrated reproducible spin transport across the interface [2]. This system offers an ideal junction to form a spin-polarised field effect transistor for example.

We also demonstrated spin-current amplification in a lateral spin-valve (LSV) using a geometrical ratchet effect [3]. Two Py nanowires were designed to be 30 nm thick and 200 nm wide bridged by a Cu nanowire (70 nm thick and 100 nm wide). Here, the central part of the Cu wire was modified into the following geometrical ratchet shapes with allowing 50 nm separation between the Py wires and the ratchets. We measured over 700% spin-current amplification for the right-angled triangles with 100 nm base and 60 nm height. By utilising these fundamental building blocks, we can also develop a large variety of new devices.

This work was partially supported by the EPSRC (EP/I000933/1 and EP/K03278X/1), Royal Society Industry Fellowship, EC (NMP3-SL-2013-604398) and JST-PRESTO.

[1] A. Hirohata and K. Takanashi, J. Phys. D: Appl. Phys. (in press).
[2] L. R. Fleet et al., Phys. Rev. B 87, 024401 (2013).
[3] R. M. Abdullah et al., J. Phys. D: Appl. Phys. 47, 482001 (2014).

Dr Atsufumi Hirohata is a Professor at the Department of Electronics in the University of York. He has over 10 years of experience in spintronics, ranging from magnetic-domain imaging to spin-current interference. Before coming to York in 2007, he was a researcher at RIKEN, a Japanese governmental research institute, where he designed a spin-current interference device. He was before working at Tohoku University and Massachusetts Institute of Technology. He received his PhD in Physics at the University of Cambridge in 2001. He was originally graduated from Keio University for his BSc and MSc studies in Physics.



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