Efficiency of ultrafast optically induced spin transfer in Heusler compounds

Steil, Daniel; Walowski, Jakob; Gerhard, F.; Kießling, T.; Ebke, Daniel; Thomas, Andy; Kubota, Takahide; Oogane, Mikihiko; Ando, Yasuo; Otto, Johannes; Mann, Andreas; Hofherr, Moritz; Elliott, Peter; Dewhurst, J. K.; Reiss, Günter; Molenkamp, Laurens W.; Aeschlimann, Martin; Cinchetti, Mirko; Münzenberg, Markus; Sharma, Sangeeta; Mathias, Stefan

doi:10.1103/physrevresearch.2.023199

Cited by 37 publications

(38 citation statements)

References 30 publications

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“…The authors of this theoretical study also predicted that the spin-selective charge transfer between distinct sites can lead to a metamagnetic phase transition, switching the magnetic order from an antiferromagnetic to a transient ferromagnetic alignment. In the last two years, a number of experiments demonstrated signatures of OISTR, both in the optical [13,14] as well as in the extreme ultraviolet (XUV) [15][16][17][18] spectral range. The latter experiments were carried out with high harmonic generation (HHG) sources and exploited the element specificity of resonant core-to-valence state transitions.…”

Section: Introductionmentioning

confidence: 99%

Element-Specific Magnetization Dynamics of Complex Magnetic Systems Probed by Ultrafast Magneto-Optical Spectroscopy

et al. 2020

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The vision to manipulate and control magnetism with light is driven on the one hand by fundamental questions of direct and indirect photon-spin interactions, and on the other hand by the necessity to cope with ever growing data volumes, requiring radically new approaches on how to write, read and process information. Here, we present two complementary experimental geometries to access the element-specific magnetization dynamics of complex magnetic systems via ultrafast magneto-optical spectroscopy in the extreme ultraviolet spectral range. First, we employ linearly polarized radiation of a free electron laser facility to demonstrate decoupled dynamics of the two sublattices of an FeGd alloy, a prerequisite for all-optical magnetization switching. Second, we use circularly polarized radiation generated in a laboratory-based high harmonic generation setup to show optical inter-site spin transfer in a CoPt alloy, a mechanism which only very recently has been predicted to mediate ultrafast metamagnetic phase transitions.

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Section: Introductionmentioning

confidence: 99%

Element-Specific Magnetization Dynamics of Complex Magnetic Systems Probed by Ultrafast Magneto-Optical Spectroscopy

et al. 2020

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“…Supplementary material: Theoretical Details: Time dependent extension of density functional theory (TD-DFT), is a fully first principles approach that has been shown to accurately describe spin dynamics on femtosecond time scales [27][28][29][30][31][32] . Underpinning this time dependent extension of DFT is the Runge-Gross theorem 24 , that guarantees for common initial states a one-to-one correspondence between timedependent external potentials and densities at all later times.…”

Section: Sum Rule For the Orbital Momentmentioning

confidence: 99%

“…Methodology: The time dependent extension of density functional theory (TD-DFT), is a fully first principles approach that has been shown to accurately describe spin dynamics on femtosecond time scales [27][28][29][30][31][32] . In order to calculate the response function at L-edge the deep lying (∼870 eV below the Fermi level) 2p states must be treated on the same footing as the valence states, and thus we employ for our calculations the state-of-the-art all-electron full-potential linearized augmented plane wave method 33 , as implemented in the Elk code 26,34 .…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of XMCD sum rules at the $L$-edge: when do they fail?

Shallcross,

Dewhurst,

Elliott

et al. 2021

Preprint

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In the highly non-equilibrium conditions of laser induced spin dynamics magnetic moments can only be obtained from the spectral information, most commonly from the spectroscopy of semi-core states using the so-called x-ray magnetic circular dichroism (XMCD) sum rules. The validity of the these sum rules in tracking femtosecond spin dynamics remains, however, an open question. Employing the time dependent extension of density functional theory (TD-DFT) we compare spectroscopically obtained moments with those directly calculated from the TD-DFT densities. We find that for experimentally typical pump pulses these two very distinct routes to the spin moment are, for Co and Ni, in excellent agreement, validating the experimental approach. However, for short and intense pulses or high fluence pulses of long duration the XMCD sum rules fail, with errors exceeding 50%. This failure persists only during the pulse and occurs when the pump pulse excites charge out of the d-band and into sp-character bands, invalidating the semi-core to d-state transitions assumed by the XMCD sum rules.

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“…This first principles approach for the ultrafast dynamics of spin and charge has been shown to accurately describe magnetic systems on femtosecond time scales 5,[17][18][19][20][21] . A time step of 2.4 attoseconds was used for time propagation (see Ref.…”

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confidence: 99%

Ab-initio study of ultrafast spin dynamics in Gdx(FeCo){1-x} alloys

Dewhurst,

Shallcross,

Radu

et al. 2021

Preprint

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Using an ultrashort laser pulse we explore ab-initio the spin dynamics of Gd x (FeCo) 1−x at femtosecond time scales. Optical excitations are found to drive charge from Fe majority d-states to the unoccupied Gd f -minority states, with f -electron character excited occupation lagging behind that of the d-electron character, leading to substantial demagnetisation of both species while leaving the global moment almost unchanged. For x > 0.33 this results in the creation of an ultrafast ferromagnetic (FM) transient by the end of the laser pulse, with the Gd demagnetization rate slower than that of Fe. For all concentrations the Gd moments begin to rotate from their ground state orientations developing in-plane moments of between 0.2-0.5 µ B . Thus, the ultrafast spin dynamics of the material captures three important ingredients of the all optical switching that occurs at much later (picosecond) times: (i) the development of a FM transient, (ii) the different rates of demagnetisation of Fe and Gd and, (iii), the breaking of the colinear symmetry of the ground state. Furthermore, several predictions are made about the behaviour of Fe-Gd alloys that can be experimentally tested and can lead to a spin-filtering device.

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Efficiency of ultrafast optically induced spin transfer in Heusler compounds

Cited by 37 publications

References 30 publications

Element-Specific Magnetization Dynamics of Complex Magnetic Systems Probed by Ultrafast Magneto-Optical Spectroscopy

Element-Specific Magnetization Dynamics of Complex Magnetic Systems Probed by Ultrafast Magneto-Optical Spectroscopy

Numerical analysis of XMCD sum rules at the $L$-edge: when do they fail?

Ab-initio study of ultrafast spin dynamics in Gdx(FeCo){1-x} alloys

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