Studying Ultrafast Magnetization Dynamics with Ultrafast Extreme Ultraviolet Light

Turgut, Emrah; Grychtol, Patrik; La-o-vorakiat, Chan; Shaw, Justin M.; Knut, Ronny; Kfir, Ofer; Zusin, Dmitry; Rudolf, Dennis; Adam, Roman; Fleicher, Avner; Mathias, Stefan; Nembach, Hans T.; Cohen, Oren; Schneider, Claus M.; Aeschlimann, Martin; Silva, Thomas J.; Kapteyn, Henry C.; Murnane, Margaret M.

doi:10.1364/ls.2014.lw5h.5

Cited by 5 publications

(6 citation statements)

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“…We now turn back to the time scales of the demagnetization. In ferromagnetic systems, the demagnetization rate is generally considered to be limited by the dissipation of angular momentum from the polarized spin system via angular momentum transfer to the lattice [5,37] or through spin transport channels [4,39,40]. In an antiferromagnet, however, the total sublattice magnetizations compensate each other and no net angular momentum needs to be conserved during ultrafast demagnetization.…”

Section: Prl 116 257202 (2016) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Itinerant and Localized Magnetization Dynamics in Antiferromagnetic Ho

et al. 2016

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Using femtosecond time-resolved resonant magnetic x-ray diffraction at the Ho L 3 absorption edge, we investigate the demagnetization dynamics in antiferromagnetically ordered metallic Ho after femtosecond optical excitation. Tuning the x-ray energy to the electric dipole (E1, 2p → 5d) or quadrupole (E2, 2p → 4f) transition allows us to selectively and independently study the spin dynamics of the itinerant 5d and localized 4f electronic subsystems via the suppression of the magnetic (2 1 3-τ) satellite peak. We find demagnetization time scales very similar to ferromagnetic 4f systems, suggesting that the loss of magnetic order occurs via a similar spin-flip process in both cases. The simultaneous demagnetization of both subsystems demonstrates strong intra-atomic 4f-5d exchange coupling. In addition, an ultrafast lattice contraction due to the release of magneto-striction leads to a transient shift of the magnetic satellite peak. DOI: 10.1103/PhysRevLett.116.257202 The manipulation of magnetic order by ultrashort light pulses is of fundamental interest in solid state research and promises high technological relevance. Since the discovery of the demagnetization of Ni in <1 ps almost two decades ago [1], the ultrafast magnetization dynamics of ferromagnetic systems has been intensely studied both experimentally and theoretically [2-6]; for a review see Refs. [7,8]. In particular, the phenomenon of ultrafast magnetization reversal recently observed in ferrimagnetic lanthanide transition metal intermetallics [8][9][10][11][12][13] has attracted much attention. In these materials a complex interaction between localized f moments in the rare-earth ions and the itinerant transition metal d electrons is thought to enable the reversal of the magnetic moment on subpicosecond time scales. The interaction leads to several unexpected phenomena such as a transient ferromagnetic state in FeCoGd [10] and ultrafast angular momentum transfer between different volumes within an inhomogeneous ferrimagnetic alloy [12].In the rare-earth metals, the magnetic exchange interaction between the large localized moments of the open 4f shells is mediated by the indirect Ruderman-Kittel-KasuyaYosida (RKKY) interaction via the itinerant 5d6s electrons, leading to a parallel alignment of the two subsystems. Depending on the details of the band structure, this interaction results in a variety of magnetically ordered ground states, ranging from ferromagnetic alignment in Gd and Tb to complex antiferromagnetic (AFM) structures in the heavier rare earths. As optical excitation directly interacts with the valence electrons and not with the localized 4f states, these systems present an ideal case to study the 4f-5d interaction directly in the time domain by separately investigating the dynamics of these two subsystems. While early experiments using x-ray magnetic circular dichroism (XMCD) and the magneto-optical Kerr effect (MOKE) on the ferromagnetic lanthanides Gd and Tb found similar demagnetization time scales of 4f and 5d electrons [14], more...

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Section: Prl 116 257202 (2016) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Itinerant and Localized Magnetization Dynamics in Antiferromagnetic Ho

et al. 2016

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“…(37) Coherent optical phonons, ultrafast demagnetization dynamics, and the excitedstate character of hematite have also been studied by table-top HHG apparatuses. (38)(39)(40) This work exploits the elemental and oxidation-state specificity of transient XUV spectroscopy. When pumped at 400 nm, the identity of the Co (Figure 2) consists of an 800 nm Ti/sapphire laser to generate high-order harmonics as the probe and to produce frequency-doubled pulses for the pump excitation, a high vacuum system with high harmonic source, toroidal focusing mirror, raster scanned sample, a variable line space grating, and an Xray charge-coupled device (CCD) camera for spectral detection after the sample.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Photo-Induced Charge Transfer and Hot Carrier Relaxation Pathways in Spinel Cobalt Oxide (Co₃O₄)

et al. 2014

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The identities of photoexcited states in thin-film Co 3 O 4 and the ultrafast carrier relaxation dynamics of Co 3 O 4 are investigated with oxidation-state-specific pump−probe femtosecond core level spectroscopy. A thin-film sample is excited near the 2.8 eV optical absorption peak, and the resulting spectral changes at the 58.9 eV M 2,3edge of cobalt are probed in transient absorption with femtosecond highorder harmonic pulses generated by a Ti/sapphire laser. The initial transient state shows a significant 2 eV redshift in the absorption edge compared to the static ground state, which indicates a reduction of the cobalt valence charge. This is confirmed by a charge transfer multiplet spectral simulation, which finds the experimentally observed extreme ultraviolet (XUV) spectrum matches the specific O 2− (2p) → Co 3+ (e g ) charge-transfer transition, out of six possible excitation pathways involving Co 3+ and Co 2+ in the mixed-valence material. The initial transient state has a power-dependent amplitude decay (190 ± 10 fs at 13.2 mJ/cm 2 ) together with a slight redshift in spectral shape (535 ± 33 fs), which are ascribed to hot carrier relaxation to the band edge. The faster amplitude decay is possibly due to a decrease of charge carrier density via an Auger mechanism, as the decay rate increases when more excitation fluence is used. This study takes advantage of the oxidation-state-specificity of time-resolved XUV spectroscopy, further establishing the method as a new approach to measure ultrafast charge carrier dynamics in condensed-phase systems.

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“…The microscopic mechanisms responsible for this photoinduced ultrafast loss of magnetic order can be classified as spin-flip scattering phenomena [2,7,8] and spin transport phenomena [9][10][11][12]. Today we know that both processes clearly contribute to the ultrafast demagnetization and that the contributions of both mechanisms depend on the details of the material system and multilayer structure [8,[12][13][14][15]. In particular, optically induced spin transport via superdiffusive spin currents [4] yields a great potential for further applications.…”

mentioning

confidence: 99%

“…While spin currents have been proven to be relevant on femtosecond time scales [11,15,16], only few details are known about the amount of optically induced spin currents or spin injection efficiency across various interfaces.…”

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confidence: 99%

Speed and efficiency of femtosecond spin current injection into a nonmagnetic material

et al. 2017

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Studying Ultrafast Magnetization Dynamics with Ultrafast Extreme Ultraviolet Light

Cited by 5 publications

References 2 publications

Itinerant and Localized Magnetization Dynamics in Antiferromagnetic Ho

Itinerant and Localized Magnetization Dynamics in Antiferromagnetic Ho

Characterization of Photo-Induced Charge Transfer and Hot Carrier Relaxation Pathways in Spinel Cobalt Oxide (Co₃O₄)

Speed and efficiency of femtosecond spin current injection into a nonmagnetic material

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Studying Ultrafast Magnetization Dynamics with Ultrafast Extreme Ultraviolet Light

Cited by 5 publications

References 2 publications

Itinerant and Localized Magnetization Dynamics in Antiferromagnetic Ho

Itinerant and Localized Magnetization Dynamics in Antiferromagnetic Ho

Characterization of Photo-Induced Charge Transfer and Hot Carrier Relaxation Pathways in Spinel Cobalt Oxide (Co3O4)

Speed and efficiency of femtosecond spin current injection into a nonmagnetic material

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Characterization of Photo-Induced Charge Transfer and Hot Carrier Relaxation Pathways in Spinel Cobalt Oxide (Co₃O₄)