Simultaneous two-color snapshot view on ultrafast charge and spin dynamics in a Fe-Cu-Ni tri-layer

Abstract

Ultrafast phenomena on a femtosecond timescale are commonly examined by pump-probe experiments. This implies multiple measurements where the sample under investigation is pumped with a short light pulse and then probed with a second pulse at various time delays to follow its dynamics. Recently, the principle of streaking extreme ultraviolet (XUV) pulses in the temporal domain has enabled recording the dynamics of a system within a single pulse. However, separate pump-probe experiments at different absorption edges still lack a unified timing, when comparing the dynamics in complex systems. Here we report on an experiment using a dedicated optical element and the two-color emission of the FERMI XUV free-electron laser to follow the charge and spin dynamics in composite materials at two distinct absorption edges, simultaneously. The sample, consisting of ferromagnetic Fe and Ni layers, separated by a Cu layer, is pumped by an infrared laser and probed by a two-color XUV pulse with photon energies tuned to the M edges of these two transition metals. The experimental geometry intrinsically avoids any timing uncertainty between the two elements and unambiguously reveals an approximately 100 fs delay of the magnetic response with respect to the electronic excitation for both Fe and Ni. This delay shows that the electronic and spin degrees of freedom are decoupled during the demagnetization process. These observations underline the importance of simultaneous investigation of the temporal response of both charge and spin in multi-component materials. In a more general scenario, the experimental approach can be extended to continuous energy ranges, promising the development of jitter-free transient absorption spectroscopy in the XUV and soft X-ray regimes.

References in corpus (12)

• Petahertz Spintronics
• Tracking Cooper Pairs in a Cuprate Superconductor by Ultrafast Angle-Resolved Photoemission
• High photon flux table-top coherent extreme ultraviolet source
• Femtosecond spin current pulses generated by the non-thermal spin-dependent Seebeck effect and interacting with ferromagnets in spin valves
• Role of Spin Flips versus Spin Transport in Non Thermal Electrons Excited by Ultrashort Optical Pulses in Transition Metals
• Spin-current-mediated rapid magnon localisation and coalescence after ultrafast optical pumping of ferrimagnetic alloys
• Influence of laser-excited electron distributions on the x-ray magnetic circular dichroism spectra: Implications for femtosecond demagnetization in Ni
• Magnetic switching in granular FePt layers promoted by near-field laser enhancement
• Analysis of the linear relationship between asymmetry and magnetic moment at the M-edge of 3d transition metals
• Single shot time-resolved magnetic x-ray absorption at a Free Electron Laser
• Laser-induced ultrafast transport and demagnetization at the earliest time: First-principles and real-time investigation
• X-ray detection of ultrashort spin current pulses in synthetic antiferromagnets

Cited by in corpus (8)

• Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL
• Electronic origin of x-ray absorption peak shifts
• Ultrafast behavior of induced and intrinsic magnetic moments in CoFeB/Pt bilayers probed by element-specific measurements in the extreme ultraviolet spectral range
• Ultrafast demagnetization in bulk nickel induced by X-ray photons tuned to Ni $M_3$ and $L_3$ absorption edges
• FEL stochastic spectroscopy revealing silicon bond softening dynamics
• Spectroscopic probe of ultrafast magnetization dynamics in the extreme ultraviolet spectral range
• Time-Resolved XUV absorption spectroscopy and magnetic circular dichroism at the Ni $M_{2,3}$-edges
• Electronic mechanism of sub-100-fs demagnetization induced by a femtosecond light pulse