Disentangling Spin and Charge Dynamics with Magneto-Optics

Carpene, E.; Boschini, Fabio; Hedayat, Hamoon; Piovera, C.; Dallera, C.; Puppin, E.; Mansurova, M.; Münzenberg, Markus; Zhang, X.; Gupta, Arunava

doi:10.1007/978-3-319-07743-7_14

Cited by 5 publications

(9 citation statements)

References 2 publications

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“…Interestingly, the separation of the charge and spin contributions to the dynamics of the off-diagonal component of the dielectric tensor ε ij [28] on the ultrafast timescale is non-trivial. Indeed, while reflectivity is given by the diagonal components ε ii , both ε ii and ε ij determine the magneto-optical coefficient α ∝ ε ij /ε ii .…”

Section: Discussionmentioning

confidence: 99%

“…Because magnetization M is real, this requires the magneto-optical coefficient to be complex as well: α = α ′ + iα ′′ = A exp(iφ). It is worth noting that the variations of magnetization δM (t) cannot change the phase of the MOKE response, and thus the variations of the latter should be understood as having an optical origin [28]. Indeed, since the magnetization M in Θ = αM is real, the phase of the complex value Θ is governed by α only.…”

Section: Towards Genuine Ultrafast Demagnetizationmentioning

confidence: 99%

“…Second, it is by now clear that an unambiguous analysis of femtosecond magneto-optical results is non-trivial, owing to the sizeable transient changes of the electron population [24,25,26]. Later it was suggested that further insights into magnetization dynamics can be obtained when using different pump and probe optical wavelengths for time-resolved MOKE [11,19], employing non-linear optical technique to address different electronic states with the pump and probe beams [27] or performing a detailed polarimetric analysis separating charge and spin contributions to time-resolved MOKE signals [28,29]. Direct accounting for the respective impact of these effects on the transient magnetization as recently demonstrated for the different probing depth of the real and imaginary part of the complex MOKE [30] represents another perspective.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the time-resolved magneto-optical Kerr effect for ultrafast magnetization dynamics in ferromagnetic thin films

Razdolski

Alekhin

Martens

et al. 2017

J. Phys.: Condens. Matter

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We discuss fundamental aspects of laser-induced ultrafast demagnetization probed by the time-resolved magneto-optical Kerr effect (MOKE). Studying thin Fe films on MgO substrate in the absence of electronic transport, we demonstrate how to disentangle pump-induced variations of magnetization and magneto-optical coefficients. We provide a mathematical formalism for retrieving genuine laser-induced magnetization dynamics and discuss its applicability in real experimental situations. We further stress the importance of temporal resolution achieved in the experiments and argue that measurements of both time-resolved MOKE rotation and ellipticity are needed for the correct assessment of magnetization dynamics on sub-picosecond timescales. The framework developed here sheds light onto the details of the timeresolved MOKE technique and contributes to the understanding of the interplay between ultrafast laser-induced optical and magnetic effects.

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Section: Discussionmentioning

confidence: 99%

Section: Towards Genuine Ultrafast Demagnetizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of the time-resolved magneto-optical Kerr effect for ultrafast magnetization dynamics in ferromagnetic thin films

Razdolski

Alekhin

Martens

et al. 2017

J. Phys.: Condens. Matter

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“…The most apparent distinction between the MOKE spectrum in our material system, when electrons are injected to GaAs optically, and the n-doped GaAs epilayer [22] is the spectral width -the MO coefficient is non-zero only within  15 meV for the latter material system (see Fig. that is necessary to measure both these quantities for disentangling the dynamics of spin and charge [28]. We observed that a few picoseconds after the photo-excitation of the sample by a pump pulse The observed spatial evolution of the (spin-sensitive) MOKE signal for time delays < 100 ps shares rather prominent similarities with the spatially-resolved time-integrated photoluminescence (PL) measured under comparable conditions in p-doped GaAs [29][30][31].…”

Section: Heterostructurementioning

confidence: 96%

Quasi-nondegenerate pump–probe magnetooptical experiment in GaAs/AlGaAs heterostructure based on spectral filtration

et al. 2020

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We report on a quasi-nondegenerate pump–probe technique that is based on spectral-filtration of femtosecond laser pulses by a pair of mutually-spectrally-disjunctive commercially available interference filters. The described technique enables to obtain pump and probe pulses with wavelengths that are spectrally close but distinct. These contradictory requirements, which are dictated, for example, by a suppression of stray pump photons from the probe beam in spin-sensitive magneto-optical experiments in non-magnetic semiconductors, can be fulfilled at very low cost and basically no requirement on space. Especially the second feature is important in pump–probe microscopy where collinear propagation of pump and probe pulses is dictated by utilization of a microscopic objective and where the setups are typically quite complex but suffer from a limited size of optical breadboards. Importantly, this spectral-filtration of 100 fs long laser pulses does not affect considerably the resulting time-resolution, which remains well below 500 fs. We demonstrate the practical applicability of this technique by performing spin-sensitive magnetooptical Kerr effect (MOKE) experiment in GaAs/AlGaAs heterostructure, where a high-mobility spin system is formed after optical injection of electrons at wavelengths close to the MOKE resonance. In particular, we studied the time- and spatial-evolutions of spin-related (MOKE) and charge-related (reflectivity) signals. We revealed that they evolve in a similar but not exactly the same way which we attributed to interplay of several electron many-body effects in GaAs.

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“…∆θ K (t)/θ K0 = ∆M (t)/M 0 [39]. Furthermore, we checked the dynamical Kerr rotation and ellipticity of all combinations of s and p pump and probe polarizations [31,40,41], and the MOKE response stayed the same in shape and amplitude, within the experimental uncertainty.…”

mentioning

confidence: 92%

Anisotropic Ultrafast Spin Dynamics in Epitaxial Cobalt

Unikandanunni,

Medapalli,

Fullerton

et al. 2020

Preprint

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We investigate the ultrafast spin dynamics in an epitaxial hcp(1 100) cobalt thin film. By performing pump-probe magneto-optical measurements with the magnetization along either the easy or hard magnetic axis, we determine the demagnetization and recovery times for the two axes. We observe a 35% slower dynamics along the easy magnetization axis, which we attribute to magneto-crystalline anisotropy of the electron-phonon coupling, supported by our ab initio calculations. This points towards an unambiguous and previously undisclosed role of anisotropic electron-lattice coupling in ultrafast magnetism.

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Disentangling Spin and Charge Dynamics with Magneto-Optics

Cited by 5 publications

References 2 publications

Analysis of the time-resolved magneto-optical Kerr effect for ultrafast magnetization dynamics in ferromagnetic thin films

Analysis of the time-resolved magneto-optical Kerr effect for ultrafast magnetization dynamics in ferromagnetic thin films

Quasi-nondegenerate pump–probe magnetooptical experiment in GaAs/AlGaAs heterostructure based on spectral filtration

Anisotropic Ultrafast Spin Dynamics in Epitaxial Cobalt

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