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Stoner versus Heisenberg: Ultrafast exchange reduction and magnon generation during laser-induced demagnetization

Journal Article · · Physical Review. B
 [1];  [2];  [3];  [4];  [2];  [5];  [2];  [2];  [5];  [5];  [6];  [7];  [8];  [2];  [2];  [2]
  1. University of Colorado, Boulder, CO (United States); JILA/University of Colorado Boulder, Boulder, CO
  2. University of Colorado, Boulder, CO (United States)
  3. VSB Technical University of Ostrava (Czech Republic); Charles University, Prague (Czech Republic)
  4. Charles University, Prague (Czech Republic); Uppsala University (Sweden)
  5. National Institute of Standards and Technology, Boulder, CO (United States)
  6. Georg-August-Universität Göttingen (Germany)
  7. University of Kaiserslautern and Research Center OPTIMAS (Germany)
  8. Uppsala University (Sweden)

Understanding how the electronic band structure of a ferromagnetic material is modified during laser-induced demagnetization on femtosecond timescales has been a long-standing question in condensed matter physics. Here, we use ultrafast high harmonics to measure time-, energy-, and angle-resolved M-edge magnetic asymmetry spectra for Co lms after optical pumping to induce ultrafast demagnetization. This provides a complete data set that we can compare with advanced ab initio magneto-optical calculations. Here, tur analysis identifies that the dominant mechanisms contributing to ultrafast demagnetization on timescales up to several picoseconds are a transient reduction in the exchange splitting and the excitation of ultrafast magnons. Surprisingly, we nd that the magnon contribution to ultrafast demagnetization is already strong on sub-picosecond timescales, while the reduction in exchange splitting persists to several picoseconds.

Research Organization:
University of Colorado, Boulder, CO (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
Grant/Contract Number:
SC0002002
OSTI ID:
1680051
Alternate ID(s):
OSTI ID: 1338086
OSTI ID: 1535807
OSTI ID: 1968486
Journal Information:
Physical Review. B, Journal Name: Physical Review. B Journal Issue: 22 Vol. 94; ISSN 2469-9950
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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Spin-orbit torque-mediated spin-wave excitation as an alternative paradigm for femtomagnetism journal September 2019
Is perpendicular magnetic anisotropy essential to all-optical ultrafast spin reversal in ferromagnets? journal September 2017
Band structure evolution during the ultrafast ferromagnetic-paramagnetic phase transition in cobalt journal March 2017
Critical behavior within 20 fs drives the out-of-equilibrium laser-induced magnetic phase transition in nickel journal March 2018
Spin Berry points as crucial for ultrafast demagnetization journal March 2021
Accelerating the laser-induced demagnetization of a ferromagnetic film by antiferromagnetic order in an adjacent layer text January 2020
Uncovering the role of the density of states in controlling ultrafast spin dynamics preprint January 2020
Spin-current-mediated rapid magnon localisation and coalescence after ultrafast optical pumping of ferrimagnetic alloys journal April 2019
Femtosecond X-ray induced changes of the electronic and magnetic response of solids from electron redistribution journal November 2019
A tunable time-resolved spontaneous Raman spectroscopy setup for probing ultrafast collective excitation and quasiparticle dynamics in quantum materials journal July 2018
Ultrafast magnetization dynamics in Nickel: impact of pump photon energy journal May 2017
Transport theory for femtosecond laser-induced spin-transfer torques journal February 2018
Ab initio theory of magnetization induced by light absorption in ferromagnets journal December 2019
Speed and efficiency of femtosecond spin current injection into a nonmagnetic material journal September 2017
Direct measurement of the static and transient magneto-optical permittivity of cobalt across the entire M -edge in reflection geometry by use of polarization scanning journal January 2018
Femtosecond tracking of carrier relaxation in germanium with extreme ultraviolet transient reflectivity journal May 2018
Spin Transfer due to Quantum Magnetization Fluctuations journal December 2017
Revealing the Nature of the Ultrafast Magnetic Phase Transition in Ni by Correlating Extreme Ultraviolet Magneto-Optic and Photoemission Spectroscopies journal August 2018
Magneto-Optical Functions at the 3 p Resonances of Fe, Co, and Ni: Ab initio Description and Experiment journal May 2019
Ultrafast optically induced spin transfer in ferromagnetic alloys journal January 2020
Spin-orbit torque-mediated spin-wave excitation as an alternative paradigm for femtomagnetism text January 2019

Figures / Tables (3)