Ultrafast demagnetization of iron induced by optical vs terahertz pulses

We study ultrafast magnetization quenching of ferromagnetic iron following excitation by an optical vs a terahertz pump pulse. While the optical pump (photon energy of 3.1 eV) induces a strongly nonthermal electron distribution, terahertz excitation (~4 meV) results in a quasi-thermal perturbation o...

Full description

Saved in:
Bibliographic Details
Published inarXiv.org
Main Authors Chekhov, A L, Behovits, Y, Heitz, J J F, Denker, C, Reiss, D A, Wolf, M, Weinelt, M, Brouwer, P W, Münzenberg, M, Kampfrath, T
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 03.06.2021
Subjects
Demagnetization
Elastic limit
Elastic scattering
Electron distribution
Electron spin
Electrons
Excitation
Ferromagnetism
Iron
Kerr magnetooptical effect
Perturbation
Photons
Spin dynamics
Online AccessGet full text

Cover

More Information
Summary:We study ultrafast magnetization quenching of ferromagnetic iron following excitation by an optical vs a terahertz pump pulse. While the optical pump (photon energy of 3.1 eV) induces a strongly nonthermal electron distribution, terahertz excitation (~4 meV) results in a quasi-thermal perturbation of the electron population. The pump-induced spin and electron dynamics are interrogated by the magneto-optic Kerr effect (MOKE). A deconvolution procedure allows us to push the time resolution down to 130 fs, even though the driving terahertz pulse is more than 0.5 ps long. Remarkably, the MOKE signals exhibit an almost identical time evolution for both optical and terahertz pump pulses, despite the three orders of magnitude different number of excited electrons. We are able to quantitatively explain our results using a model based on quasi-elastic spin-flip scattering. It shows that in the small-perturbation limit, the rate of demagnetization of a metallic ferromagnet is proportional to the excess energy of the electrons, independent of the precise shape of their distribution. Our results reveal that the dynamics of ultrafast demagnetization and of the closely related terahertz spin transport do not depend on the pump photon energy.
ISSN:2331-8422