We show that the magnetization of a thin ferromagnetic (Ga,Mn)As layer can be modulated by picosecond acoustic pulses. In this approach a picosecond strain pulse injected into the structure induces a tilt of the magnetization vector M, followed by the precession of M around its equilibrium orientation. This effect can be understood in terms of changes in magnetocrystalline anisotropy induced by the pulse. A model where only one anisotropy constant is affected by the strain pulse provides a good description of the observed time-dependent response.

We demonstrate selective excitation of a spin wave mode in a ferromagnetic (Ga,Mn)As film by picosecond strain pulses. For a certain range of magnetic fields applied in the layer plane only a single frequency is detected for the magnetization precession. We explain this selectivity of spin mode excitation by the necessity of spatial matching of magnon and phonon eigenfunctions, which represents a selection rule analogous to momentum conservation for magnon-phonon interaction in bulk ferromagnetic materials.

. (2016) Ultrafast changes of magnetic anisotropy driven by laser-generated coherent and noncoherent phonons in metallic films. Physical Review B, 93 (21 A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. ABSTRACTUltrafast optical excitation of a metal ferromagnetic film results in a modification of the magnetocrystalline anisotropy and induces the magnetization precession. We consider two main contributions to these processes: an effect of non-coherent phonons, which modifies the temperature dependent parameters of the magneto-crystalline anisotropy; and coherent phonons in the form of a strain contributing via inverse magnetostriction. Contrary to the earlier experiments with high symmetry ferromagnetic structures, where these mechanisms could not be separated, we study the magnetization response to femtosecond optical pulses in the low-symmetry magnetostrictive Galfenol film so that it is possible to separate the coherent and non-coherent phonon contributions. By choosing certain experimental geometry and external magnetic field, we can distinguish the contribution from a specific mechanism. Theoretical analysis and numerical calculations are used to support the experimental observations and proposed model.