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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 Article · · Physical Review B
 [1];  [2];  [2];  [2];  [2];  [2];  [3];  [4];  [4];  [4];  [5];  [2];  [2]
  1. University of Colorado, Boulder, CO (United States); JILA/University of Colorado
  2. University of Colorado, Boulder, CO (United States)
  3. VSB Technical University Ostrava (Czech-Republic)
  4. National Institute of Standards and Technology, Boulder, CO (United States)
  5. Uppsala University (Sweden)
+ Show Author Affiliations

The microscopic state of a magnetic material is characterized by its resonant magneto-optical response through the off-diagonal dielectric tensor component εxy. However, the measurement of the full complex εxy in the extreme ultraviolet spectral region covering the M absorption edges of 3d ferromagnets is challenging due to the need for either a careful polarization analysis, which is complicated by a lack of efficient polarization analyzers, or scanning the angle of incidence in fine steps. Here, we propose and demonstrate a technique to extract the complex resonant permittivity εxy simply by scanning the polarization angle of linearly polarized high harmonics to measure the magneto-optical asymmetry in reflection geometry. Because this technique is more practical and faster to experimentally implement than previous approaches, we can directly measure the full time evolution of εxy (t) during laser-induced demagnetization across the entire M2,3 absorption edge of cobalt with femtosecond time resolution. We find that for polycrystalline Co films on an insulating substrate, the changes in εxy are uniform throughout the spectrum, to within our experimental precision. This result suggests that, in the regime of strong demagnetization, the ultrafast demagnetization response is primarily dominated by magnon generation. Here, we estimate the contribution of exchange-splitting reduction to the ultrafast demagnetization process to be no more than 25%.

Research Organization:
University of Colorado, Boulder, CO (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; Gordon and Betty Moore Foundation; Knut and Alice Wallenberg Foundation
Grant/Contract Number:
SC0002002
OSTI ID:
1678732
Alternate ID(s):
OSTI ID: 1418717
OSTI ID: 1540762
OSTI ID: 1957815
Journal Information:
Physical Review B, Journal Name: Physical Review B Journal Issue: 2 Vol. 97; ISSN 2469-9950
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (4)

Femtosecond X-ray induced changes of the electronic and magnetic response of solids from electron redistribution journal November 2019
Femtosecond tracking of carrier relaxation in germanium with extreme ultraviolet transient reflectivity journal May 2018
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

Figures / Tables (10)

FIG. 1(p. 5)figure FIG. 1
FIG. 2(p. 7)figure FIG. 2
FIG. 3.(p. 8)figure FIG. 3.
FIG. 4(p. 9)figure FIG. 4
FIG. 5(p. 10)figure FIG. 5
FIG. 6(p. 11)figure FIG. 6
FIG. 7(p. 12)figure FIG. 7
FIG. 8(p. 13)figure FIG. 8
FIG. 9.(p. 20)figure FIG. 9.
FIG. 10(p. 22)figure FIG. 10

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Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
Magnetic multilayers
Magnetic techniques
Magnetism
Magnetization switching
Magneto-optical Kerr effect
Magneto-optical effect
Magneto-optical spectra
Optical absorption spectroscopy
Surface magneto-optical Kerr effect
Ultrafast phenomena
Ultrafast pump-probe spectroscopy