Ultrafast magnetostriction and phonon-mediated stress in a photoexcited ferromagnet

Femtosecond excitation of SrRuO₃ nanolayers in a SrRuO₃/SrTiO₃ superlattice quenches their ferromagnetism, resulting in magnetostriction. The buildup of mechanical stress is observed in real time by mapping lattice motions via ultrafast x-ray diffraction. A rise time of 500 fs is found for a wide range of excitation wavelengths. In the ferromagnetic phase, phonon-mediated (σₚₕ) and magnetostrictive stress (σM) components display similar strengths but opposite signs. The amplitude of σM follows the temperature dependent magnetization M²(T) whereas the strength of σₚₕ is determined by the amount of deposited energy.