| 1. |
- Tengdin, Phoebe, et al.
(författare)
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Direct light–induced spin transfer between different elements in a spintronic Heusler material via femtosecond laser excitation
- 2020
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Ingår i: Science Advances. - : American Association for the Advancement of Science. - 2375-2548. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- Heusler compounds are exciting materials for future spintronics applications because they display a wide range of tunable electronic and magnetic interactions. Here, we use a femtosecond laser to directly transfer spin polarization from one element to another in a half-metallic Heusler material, Co2MnGe. This spin transfer initiates as soon as light is incident on the material, demonstrating spatial transfer of angular momentum between neighboring atomic sites on time scales < 10 fs. Using ultrafast high harmonic pulses to simultaneously and independently probe the magnetic state of two elements during laser excitation, we find that the magnetization of Co is enhanced, while that of Mn rapidly quenches. Density functional theory calculations show that the optical excitation directly transfers spin from one magnetic sublattice to another through preferred spin-polarized excitation pathways. This direct manipulation of spins via light provides a path toward spintronic devices that can operate on few-femtosecond or faster time scales.
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| 2. |
- Zusin, Dmitriy, et al.
(författare)
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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
- 2018
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 97:2
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Tidskriftsartikel (refereegranskat)abstract
- The microscopic state of amagnetic material is characterized by its resonant magneto-optical response through the off-diagonal dielectric tensor component epsilon(xy). However, the measurement of the full complex epsilon(xy) 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 epsilon(xy) 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 epsilon(xy)(t) during laser-induced demagnetization across the entire M-2,M-3 absorption edge of cobalt with femtosecond time resolution. We find that for polycrystalline Co films on an insulating substrate, the changes in epsilon(xy) 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. We estimate the contribution of exchange-splitting reduction to the ultrafast demagnetization process to be no more than 25%.
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