Dynamics of the MnAs α/β-Striped Microstructure and of the Fe Magnetization Reversal in Fe/MnAs/GaAs(001): An Optical-Laser Pump–Free-Electron-Laser Probe Scattering Experiment

Abstract

It was shown recently that the Fe magnetization reversal in the Fe/MnAs/GaAs(001) epitaxial system, attained by temperature control of the regular stripe pattern of the MnAs α-and β-phases, can also be driven by an ultrashort optical laser pulse. In the present time-resolved scattering experiment, we address the dynamics of the MnAs α-β self-organized stripe pattern induced by a 100 fs optical laser pulse, using as a probe the XUV radiation from the FERMI free-electron laser. We observe a loss in the diffraction intensity from the ordered α-β stripes that occurs at two characteristic timescales in the range of~10 −12 and~10 −10 s. We associate the first intensity drop with ultrafast electron-lattice energy exchange processes within the laser-MnAs interaction volume and the second with thermal diffusion towards the MnAs/GaAs interface. With the support of model calculations, the observed dynamics are interpreted in terms of the

Threshold MnAs thickness for the formation of ordered α/β stripes in MnAs/GaAs(001)

“…What one actually does by changing the temperature is to control the surface dipolar fields associated with the template magnetic microstructure, and, ultimately, vary the effective magnetic field acting on the overlayer. Time-resolved experiments showed the potential of this approach for fast magnetization switching, where the microstructure changes are triggered by a single femtosecond optical laser pulse [17,18].…”

“…A shorter period should also favor a better spatial definition of the TIMS process, since the size of the smallest bit of the overlayer that one can envisage switching independently is proportional to the period. Secondly, it was shown that a fluence threshold exists for laser induced switching, which corresponds to the complete transition of the MnAs film into the high temperature β phase [17,18]. Therefore a thinner MnAs template should make it possible to switch the overlayer magnetization using lower laser fluence, i.e.…”