Optimum excitation wavelength and photon energy threshold for spintronic terahertz emission from Fe/Pt bilayer

Valynn Katrine Mag-usara; Mary Clare Escaño; Christopher E. Petoukhoff; Garik Torosyan; Laura Scheuer; Julien Madéo; Jessica Afalla; Miezel L. Talara; Joselito E. Muldera; Hideaki Kitahara; David R. Bacon; Makoto Nakajima; Keshav Dani; Evangelos Th. Papaioannou; René Beigang; Masahiko Tani

iScience (Jul 2022)

Optimum excitation wavelength and photon energy threshold for spintronic terahertz emission from Fe/Pt bilayer

Valynn Katrine Mag-usara,
Mary Clare Escaño,
Christopher E. Petoukhoff,
Garik Torosyan,
Laura Scheuer,
Julien Madéo,
Jessica Afalla,
Miezel L. Talara,
Joselito E. Muldera,
Hideaki Kitahara,
David R. Bacon,
Makoto Nakajima,
Keshav Dani,
Evangelos Th. Papaioannou,
René Beigang,
Masahiko Tani

Affiliations

Valynn Katrine Mag-usara: Research Center for Development of Far-infrared Region, University of Fukui, Fukui 910-8507, Japan; Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871, Japan; Corresponding author
Mary Clare Escaño: Research Center for Development of Far-infrared Region, University of Fukui, Fukui 910-8507, Japan
Christopher E. Petoukhoff: Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan; KAUST Solar Center, Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
Garik Torosyan: Photonic Center Kaiserslautern, Kaiserslautern 67663, Germany
Laura Scheuer: Department of Physics, Technical University of Kaiserslautern, Kaiserslautern 67663, Germany
Julien Madéo: Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan
Jessica Afalla: Research Center for Development of Far-infrared Region, University of Fukui, Fukui 910-8507, Japan; Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan
Miezel L. Talara: Research Center for Development of Far-infrared Region, University of Fukui, Fukui 910-8507, Japan
Joselito E. Muldera: Research Center for Development of Far-infrared Region, University of Fukui, Fukui 910-8507, Japan
Hideaki Kitahara: Research Center for Development of Far-infrared Region, University of Fukui, Fukui 910-8507, Japan
David R. Bacon: Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan
Makoto Nakajima: Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871, Japan
Keshav Dani: Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan
Evangelos Th. Papaioannou: Institute of Physics, Martin Luther University of Halle-Wittenberg, Halle 06108, Germany
René Beigang: Department of Physics, Technical University of Kaiserslautern, Kaiserslautern 67663, Germany
Masahiko Tani: Research Center for Development of Far-infrared Region, University of Fukui, Fukui 910-8507, Japan

Journal volume & issue: Vol. 25, no. 7
p. 104615

Abstract

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Summary: Terahertz emission from ferromagnetic/non-magnetic spintronic heterostructures had been demonstrated as pump wavelength-independent. We report, however, the pump wavelength dependence of terahertz emission from an optimized Fe/Pt spintronic bilayer on MgO substrate. Maximum terahertz generation per total pump power was observed in the 1200- to 1800-nm pump wavelength range, and a marked decrease in the terahertz emission efficiency beyond 2500 nm (pump photon energies <0.5 eV) suggests a ∼0.35-eV threshold pump photon energy for effective spintronic terahertz emission. The inferred threshold is supported by previous theoretical results on the onset energy of significant spin-filtering at the Fe-Pt interface, and confirmed by Fe/Pt electronic structure calculations in this present work. The results of terahertz time-domain emission spectroscopy show the sensitivity of spintronic terahertz emission to both the optical absorptance of the heterostructure and the energy-dependent spin transport, as dictated by the properties of the metallic thin films.

Published in iScience

ISSN: 2589-0042 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Science
Website: http://www.cell.com/iscience/home

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