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Proceedings Paper

Helicity-dependent THz-emission in thin film Co/Pt bilayers: role of the interface (Conference Presentation)
Author(s): Rajasekhar Medapalli; Guanqiao Li; Rostislav Mikhaylovskiy; Fred Spada; Thomas J. Silva; Theo Rasing; Alexey Kimel; Eric E. Fullerton
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Paper Abstract

Generating and controlling spin currents at magnetic/nonmagnetic layer interfaces using ultrashort laser pulses has triggered the development of new high- operational frequency spintronic devices. Recent studies showed that laser-driven spin currents and opto-magnetic torques acting on spins are most effective when an interface is created between ferromagnetic Co and nonmagnetic Pt thin films. Our study focuses on the role of the Co-Pt interface on laser-induced optical torques in the strongly spin-orbit coupled Co/Pt model system. We varied the average roughness at the interface, in the range of 0.1-1.0 nm, by tuning the deposition pressure conditions during fabrication. With the aid of time-resolved THz-emission spectroscopy we detected both the laser-induced helicity-independent(HI) and helicity-dependent(HD) THz-emission due to spin-Hall and spin-orbit torque effects, respectively. We reveal a dramatic change in the detected THz-signals when the interface roughness is varied. For example, the HD-THz emission is observed only when the roughness is 0.3 nm or above. To study the role of intermixing a CoPt spacer layer, with varying compositions, is introduced at the interface. However, the detected THz-emission signals rule out the intermixing effects in determining the helicity-dependence. Moreover, static spin-hall conductivity measurements provide with new insights in understanding the role of spin-orbit coupling, at the Co/Pt interfaces, in laser-induced optical torques on net magnetization. This research is funded by DOE:DE-SC001823

Paper Details

Date Published: 18 September 2018
Proc. SPIE 10732, Spintronics XI, 107322W (18 September 2018); doi: 10.1117/12.2321641
Show Author Affiliations
Rajasekhar Medapalli, Univ. of California, San Diego (United States)
Guanqiao Li, Radboud Univ. Nijmegen (Netherlands)
Rostislav Mikhaylovskiy, Radboud Univ. Nijmegen (Netherlands)
Fred Spada, Univ. of California, San Diego (United States)
Thomas J. Silva, National Institute of Standards and Technology (United States)
Theo Rasing, Radboud Univ. Nijmegen (Netherlands)
Alexey Kimel, Radboud Univ. Nijmegen (Netherlands)
Eric E. Fullerton, Univ. of California, San Diego (United States)

Published in SPIE Proceedings Vol. 10732:
Spintronics XI
Henri-Jean Drouhin; Jean-Eric Wegrowe; Manijeh Razeghi; Henri Jaffrès, Editor(s)

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