Phoebe M. Tengdin
EPFL
Heusler compounds are exciting materials for future spintronics applications because they display a wide range of tunable electronic and magnetic interactions such as metallicity, superconductivity, and giant magneto-resistance. However, the ultimate speed at which spins can be manipulated in materials is still an open question. In this work, we use a femtosecond light pulse to directly transfer spin polarization from one element to another in a half-metallic Heusler material, Co2MnGe. This spin transfer initiates as soon as light is incident on the material, showing that we can spatially transfer angular momentum between neighboring atomic sites on timescales less than 10 fs. Using ultrafast high harmonic pulses to simultaneously and independently probe the magnetic state of two elements during laser excitation, we find that the magnetization of Co is enhanced, while that of Mn rapidly quenches. By comparing our measurements to density functional theory, we show that the optical excitation directly transfers spin from one magnetic sub-lattice to another, via preferred spin-polarized excitation pathways. This direct manipulation of spins via light provides a path towards spintronic logic devices such as switches that can operate on few femtosecond or even faster timescales.