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Coherent and incoherent ultrafast magnetization dynamics in 3d ferromagnets driven by extreme terahertz fields

Coherent and incoherent ultrafast magnetization dynamics in 3d ferromagnets driven by extreme terahertz fields

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SHALABY, Mostafa, Andreas DONGES, Karel CARVA, Rolf ALLENSPACH, Peter M. OPPENEER, Ulrich NOWAK, Christoph P. HAURI, 2018. Coherent and incoherent ultrafast magnetization dynamics in 3d ferromagnets driven by extreme terahertz fields. In: Physical Review B. 98(1), 014405. ISSN 2469-9950. eISSN 2469-9969. Available under: doi: 10.1103/PhysRevB.98.014405

@article{Shalaby2018-07-03Coher-42997, title={Coherent and incoherent ultrafast magnetization dynamics in 3d ferromagnets driven by extreme terahertz fields}, year={2018}, doi={10.1103/PhysRevB.98.014405}, number={1}, volume={98}, issn={2469-9950}, journal={Physical Review B}, author={Shalaby, Mostafa and Donges, Andreas and Carva, Karel and Allenspach, Rolf and Oppeneer, Peter M. and Nowak, Ulrich and Hauri, Christoph P.}, note={Article Number: 014405} }

Shalaby, Mostafa Hauri, Christoph P. 2018-07-03 Nowak, Ulrich Allenspach, Rolf Nowak, Ulrich Ultrafast spin dynamics in magnetic materials is generally associated with ultrafast heating of the electronic system by a near infrared femtosecond laser pulse, thus offering only an indirect and nonselective access to the spin order. Here we explore spin dynamics in ferromagnets by means of extremely intense THz pulses, as at these low frequencies the magnetic field provides a direct and selective route to coherently control the magnetization. We find that, at low fields, the observed off-resonantly excited spin precession is phase locked to the THz magnetic field. At extreme THz fields, the coherent spin dynamics become convoluted with an ultrafast incoherent magnetic quenching due to the absorbed energy. This demagnetization takes place upon a single shot exposure. The magnetic properties are found to be permanently modified above a THz pump fluence of ≈100mJ/cm<sup>2</sup>. We conclude that magnetization switching cannot be reached. Our atomistic spin-dynamics simulations excellently explain the measured magnetization response. We find that demagnetization driven by THz laser-field coupling to electron charges occurs, suggesting nonconducting materials for achieving coherent THz-magnetization reversal. terms-of-use 2018-08-07T12:20:43Z eng Carva, Karel Donges, Andreas Hauri, Christoph P. Oppeneer, Peter M. Shalaby, Mostafa 2018-08-07T12:20:43Z Carva, Karel Coherent and incoherent ultrafast magnetization dynamics in 3d ferromagnets driven by extreme terahertz fields Oppeneer, Peter M. Donges, Andreas Allenspach, Rolf

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