Néel vector switching and terahertz spin-wave excitation in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Mn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>Au</mml:mi></mml:mrow></mml:math> due to femtosecond spin-transfer torques
Markus Weißenhofer, Francesco Foggetti, U. Nowak, Peter M. Oppeneer
Abstract
Efficient and fast manipulation of antiferromagnets has to date remained a challenging task, hindering their application in spintronic devices. For ultrafast operation of such devices, it is highly desirable to be able to control the antiferromagnetic order within picoseconds---a timescale that is difficult to achieve with electrical circuits. Here, we demonstrate that bursts of spin-polarized hot-electron currents emerging due to laser-induced ultrafast demagnetization are able to efficiently excite spin dynamics in antiferromagnetic ${\mathrm{Mn}}_{2}\mathrm{Au}$ by exerting a spin-transfer torque on femtosecond timescales. We combine quantitative superdiffusive transport and atomistic spin-model calculations to describe a spin-valve-type trilayer consisting of $\mathrm{Fe}|\mathrm{Cu}|{\mathrm{Mn}}_{2}\mathrm{Au}$. Our results demonstrate that femtosecond spin-transfer torques can switch the ${\mathrm{Mn}}_{2}\mathrm{Au}$ layer within a few picoseconds. In addition, we find that spin waves with high frequencies up to several THz can be excited in ${\mathrm{Mn}}_{2}\mathrm{Au}$.