Ultrafast three-dimensional magnetization precession and magnetic anisotropy of a photoexcited thin film of iron

Abstract

We investigated the three-dimensional dynamics of the magnetization vector launched by an intense infrared pulse of femtosecond duration in a thin Fe film. We demonstrate how a single experiment of time-resolved magneto-optical Kerr effect can provide quantitative information on the temporal evolution of the magnetization trajectory. Our approach allows us to follow the precessional motion of the magnetization and to retrieve the modulus and orientation of the magnetocrystalline anisotropy field as a function of time—and therefore of the local temperature—providing a direct experimental evidence of the phenomenological mechanism triggering the magnetization precession

Ultrafast changes of magnetic anisotropy driven by laser-generated coherent and noncoherent phonons in metallic films

“…In accordance with the model proposed by van Kampen et al [18] and followed by a number of works [7][8][9][10][11]19], we assume that the femtosecond laser pulse launches the magnetization precession by modifying the magnetic anisotropy and, thus, tilting the effective magnetic field Beff.…”

“…Due to electron-phonon interaction this process takes place on subpicosecond time scale and often may be considered as an instantaneous rise of the lattice temperature T. The increase of T affects the values of the MCA parameters and Beff tilts from its equilibrium position. Such a scenario has been considered in a number of previous works and may be attributed to the modulation of MCA by non-coherent phonons generated as a result of optical excitation [7][8][9][10][11].…”

“…Contrary to earlier works [7][8][9][10][11]13,18,19], where the optically induced precession was studied, we use a ferromagnetic film with low symmetry orientation. It is important that we use the experimental geometry, which allows us to exclude the ultrafast demagnetization as a stimulus for the excitation of magnetization precession [7,18,19] leaving only the changes of MCA as the main mechanisms for launching the precession.…”

“…[14,15] and Ref. [7][8][9][10][11] respectively, but there is no way to compare quantitatively the contributions of these mechanisms to changes of the MCA as a result of direct optical excitation.…”

Laser induced spin precession in highly anisotropic granular L1 FePt

“…[5][6][7] For ferromagnetic materials, another mechanism of reversible switching of the magnetization was suggested. 8,9 In this mechanism, the switching proceeds via coherent spin precession triggered by a subpicosecond laser pulse.…”