Magnetic switching in granular FePt layers promoted by near-field laser enhancement

Abstract

Light-matter interaction at the nanoscale in magnetic materials is a topic of intense research in view of potential applications in next-generation high-density magnetic recording. Laser-assisted switching provides a pathway for overcoming the material constraints of high-anisotropy and high-packing density media, though much about the dynamics of the switching process remains unexplored. We use ultrafast small-angle x-ray scattering at an x-ray free-electron laser to probe the magnetic switching dynamics of FePt nanoparticles embedded in a carbon matrix following excitation by an optical femtosecond laser pulse. We observe that the combination of laser excitation and applied static magnetic field, one order of magnitude smaller than the coercive field, can overcome the magnetic anisotropy barrier between "up" and "down" magnetization, enabling magnetization switching. This magnetic switching is found to be inhomogeneous throughout the material, with some individual FePt nanoparticles neither switching nor demagnetizing. The origin of this behavior is identified as the near-field modification of the incident laser radiation around FePt nanoparticles. The fraction of not-switching nanoparticles is influenced by the heat flow between FePt and a heat-sink layer.

References in corpus (7)

• All-optical control of ferromagnetic thin films and nanostructures
• Speed limit of FePt spin dynamics on femtosecond timescales
• Model for multi-shot all-thermal all-optical switching in ferromagnets
• Sub-diffraction sub-100 ps all-optical magnetic switching by passive wavefront shaping
• Accumulative magnetic switching of ultra-high-density recording media by circularly polarized light
• All-optical switching in granular ferromagnets caused by magnetic circular dichroism
• Optical energy optimization at the nanoscale by near-field interference

Cited by in corpus (11)

• The Ultrafast Einstein-De Haas Effect
• Spin-current-mediated rapid magnon localisation and coalescence after ultrafast optical pumping of ferrimagnetic alloys
• All-optical switching on the nanometer scale excited and probed with femtosecond extreme ultraviolet pulses
• Plasmon-induced demagnetization and magnetic switching in nickel nanoparticle arrays
• Simultaneous two-color snapshot view on ultrafast charge and spin dynamics in a Fe-Cu-Ni tri-layer
• Finite size effects on the ultrafast remagnetization dynamics of FePt
• Accelerating the laser-induced phase transition in nanostructured FeRh via plasmonic absorption
• Beyond a phenomenological description of magnetostriction
• Single femtosecond laser pulse excitation of individual cobalt nanoparticles
• Exploring the impact of the inverse Faraday effect on all-optical helicity-dependent magnetization switching
• Non-equilibrium self-assembly of spin-wave solitons in FePt nanoparticles