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

Razdolski, Ilya; Alekhin, Alexandr; Martens, Ulrike; Bürstel, Damian; Diesing, Detlef; Münzenberg, Markus; Bovensiepen, Uwe; Melnikov, Alexey

doi:10.1088/1361-648x/aa63c6

Cited by 44 publications

(52 citation statements)

References 45 publications

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“…High optical reflectance ensures the absence of excited carriers in Au providing much larger Δf than in the thermal case. Excited into the sp band of Fe [14,24] Fig. 1(c)].…”

mentioning

confidence: 99%

Femtosecond Spin Current Pulses Generated by the Nonthermal Spin-Dependent Seebeck Effect and Interacting with Ferromagnets in Spin Valves

Alekhin¹,

Razdolski²,

Ilin³

et al. 2017

Phys. Rev. Lett.

104

120

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Using the sensitivity of optical second harmonic generation to currents, we demonstrate the generation of 250-fs long spin current pulses in Fe=Au=Fe=MgOð001Þ spin valves. The temporal profile of these pulses indicates ballistic transport of hot electrons across a sub-100 nm Au layer. The pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Considering the calculated spin-dependent Fe=Au interface transmittance we conclude that a nonthermal spin-dependent Seebeck effect is responsible for the generation of ultrashort spin current pulses. The demonstrated rotation of spin polarization of hot electrons upon interaction with noncollinear magnetization at Au=Fe interfaces holds high potential for future spintronic devices. DOI: 10.1103/PhysRevLett.119.017202 Optimization and control of spin currents (SC) and their interaction with magnetic constituents in heterostructures on a femtosecond time scale is key for future terahertz spintronics applications. Although electronic transport through a ferromagnet (FM), as described by Mott's two current model [1], generates a spin-polarized current, its density is intrinsically limited by Joule losses. The discovery of the spin-dependent Seebeck effect (SdSE), where thermal gradients over a bulk FM [2] or across an interface to a normal metal [3] generate SCs, opened a path towards overcoming such limitations. Indeed, shortlived thermal gradients can produce short (∼100 ps) SC pulses at densities exceeding the static Joule limit, as recently demonstrated upon laser excitation of spin-valve structures [4].Creating highly energetic electrons [5][6][7][8][9], femtosecond laser excitation is promising for SC pulse generation on subpicosecond time scales, before the electron-electron [9] and electron-lattice [8] equilibration is reached.

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“…High optical reflectance ensures the absence of excited carriers in Au providing much larger Δf than in the thermal case. Excited into the sp band of Fe [14,24] Fig. 1(c)].…”

mentioning

confidence: 99%

Femtosecond Spin Current Pulses Generated by the Nonthermal Spin-Dependent Seebeck Effect and Interacting with Ferromagnets in Spin Valves

Alekhin¹,

Razdolski²,

Ilin³

et al. 2017

Phys. Rev. Lett.

104

120

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“…www.nature.com/scientificreports www.nature.com/scientificreports/ mechanisms involved with Elliot-Yafet scattering 10,[41][42][43] and spin current 6,7,11,44 have been discussed. Very recently, a quantitative study and comparison between fluence-dependent experiments and a model that includes non-equilibrium effects microscopically has been reported 45 . This investigation revealed that the non-thermal electron contribution could be another critical mechanism in understanding ultrafast photoinduced spin dynamics.…”

Section: Discussionmentioning

confidence: 99%

Role of non-thermal electrons in ultrafast spin dynamics of ferromagnetic multilayer

Shim

Syed

Kim

et al. 2020

Sci Rep

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Understanding of ultrafast spin dynamics is crucial for future spintronic applications. In particular, the role of non-thermal electrons needs further investigation in order to gain a fundamental understanding of photoinduced demagnetization and remagnetization on a femtosecond time scale. We experimentally demonstrate that non-thermal electrons existing in the very early phase of the photoinduced demagnetization process play a key role in governing the overall ultrafast spin dynamics behavior. We simultaneously measured the time-resolved reflectivity (TR-R) and the magneto-optical Kerr effect (TR-MOKE) for a Co/Pt multilayer film. By using an extended three-temperature model (E3TM), the quantitative analysis, including non-thermal electron energy transfer into the subsystem (thermal electron, lattice, and spin), reveals that energy flow from non-thermal electrons plays a decisive role in determining the type I and II photoinduced spin dynamics behavior. Our finding proposes a new mechanism for understanding ultrafast remagnetization dynamics.

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“…The precession amplitudes are obtained from the absolute values of the KR angle in the transient KR signals 12 . The field-independent small amplitude background, which is due to the response of the electron system and not related to the magnetization 21 , has been subtracted from the experimental values. At W = 100 mW the precession amplitude reaches 0.1% of the saturation magnetization M 0 .…”

Section: Discussionmentioning

confidence: 99%

Resonant thermal energy transfer to magnons in a ferromagnetic nanolayer

et al. 2020

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Energy harvesting is a concept which makes dissipated heat useful by transferring thermal energy to other excitations. Most of the existing principles are realized in systems which are heated continuously. We present the concept of high-frequency energy harvesting where the dissipated heat in a sample excites resonant magnons in a thin ferromagnetic metal layer. The sample is excited by femtosecond laser pulses with a repetition rate of 10 GHz, which results in temperature modulation at the same frequency with amplitude~0.1 K. The alternating temperature excites magnons in the ferromagnetic nanolayer which are detected by measuring the net magnetization precession. When the magnon frequency is brought onto resonance with the optical excitation, a 12-fold increase of the amplitude of precession indicates efficient resonant heat transfer from the lattice to coherent magnons. The demonstrated principle may be used for energy harvesting in various nanodevices operating at GHz and sub-THz frequency ranges.

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

Cited by 44 publications

References 45 publications

Femtosecond Spin Current Pulses Generated by the Nonthermal Spin-Dependent Seebeck Effect and Interacting with Ferromagnets in Spin Valves

Femtosecond Spin Current Pulses Generated by the Nonthermal Spin-Dependent Seebeck Effect and Interacting with Ferromagnets in Spin Valves

Role of non-thermal electrons in ultrafast spin dynamics of ferromagnetic multilayer

Resonant thermal energy transfer to magnons in a ferromagnetic nanolayer

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