Laser-induced magnetization precession in individual magnetoelastic domains of a multiferroic $\mathrm{CoFeB/BaTiO_3}$ composite

Using a magneto-optical pump-probe technique with micrometer spatial resolution we show that magnetization precession can be launched in individual magnetic domains imprinted in a $\mathrm{Co_{40}Fe_{40}B_{20}}$ (CoFeB) layer by elastic coupling to ferroelectric domains in a BaTiO$_{3}$ substrate. The dependence of the precession parameters on external magnetic field strength and orientation reveals that laser-induced ultrafast partial quenching of the magnetoelastic coupling parameter of CoFeB by $\sim$15% along with 5% ultrafast demagnetization trigger the magnetization precession. The relation between laser-induced reduction of the magnetoelastic coupling and the demagnetization can be well approximated by the $n(n+1)/2$-law with $n=2$ corresponding to the uniaxial anisotropy, confirming the thermal origin of the laser-induced anisotropy change. The excitation process in an individual magnetoelastic domain is found to be unaffected by neighboring domains. This makes laser-induced changes of magnetoelastic anisotropy a promising tool for driving magnetization dynamics in composite multiferroics with spatial selectivity.