Microscopic insights to spin transport–driven ultrafast magnetization dynamics in a Gd/Fe bilayer

Abstract

Laser-induced spin transport is a key ingredient in ultrafast spin dynamics. However, it remains debated to what extent ultrafast magnetization dynamics generates spin currents and vice versa. We use time- and spin-resolved photoemission spectroscopy to study an antiferromagnetically coupled Gd/Fe bilayer, a prototype system for all-optical switching. Spin transport leads to an ultrafast drop of the spin polarization at the Gd surface, demonstrating angular-momentum transfer over several nanometers. Thereby, Fe acts as spin filter, absorbing spin majority but reflecting spin minority electrons. Spin transport from Gd to Fe was corroborated by an ultrafast increase of the Fe spin polarization in a reversed Fe/Gd bilayer. In contrast, for a pure Gd film, spin transport into the tungsten substrate can be neglected, as spin polarization stays constant. Our results suggest that ultrafast spin transport drives the magnetization dynamics in Gd/Fe and reveal microscopic insights into ultrafast spin dynamics.

Using single and double laser pulses on the molecular Ni4@C48H36 system to design integrated nanospintronic units

“…[17][18][19] Magnetic molecules and heterostructures [20][21][22][23][24] are promising systems for future spintronic devices [25][26][27] since their discrete energy levels facilitate the manipulation of magnetization states. 28 Moreover, combining molecular spintronics with ultrafast spin dynamics [29][30][31][32][33][34] can increase storage density and information processing rates. 35 Beaurepaire et al triggered the field of optically driven spin dynamics in ferromagnetic nickel (Ni) in 1996.…”

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“…Pure electron/spin current is currently considered to be a conventional method for manipulating ferromagnetism [15][16][17][18][19][20][21][22][23][24][25]. However, it suffers from a large interfacial current density (ranging from 10 11 to 10 12 A/m 2 ) due to its low spin-current conversion efficiency.…”