Ultrafast spin injection across magnetic/nonmagnetic (FM/NM) interfaces represents a pivotal mechanism for spintronic applications, yet the governing principles of interlayer-mediated spin dynamics remain elusive. Herein, we systematically investigate femtosecond-scale spin transfer in $\mathrm{Cr}{X}_3/\mathrm{W}{Z}_2 \left(X=\mathrm{Br},\mathrm{I};Z=\mathrm{S},\mathrm{Se}\right)$ van der Waals heterostructures through combined first-principles calculations and nonadiabatic molecular dynamics simulations. Our results demonstrate that asymmetric interlayer charge transfer, accompanied by spin-flip processes, mediates ultrafast (9–27-fs) spin injection from FM $\mathrm{Cr}{X}_3$ to NM $\mathrm{W}{Z}_2$ layers. Crucially, the magnetic moment persistence in NM layers exhibits material-dependent lifetimes $\left(\mathrm{CrB}{\mathrm{r}}_3/\mathrm{WS}{\mathrm{e}}_2>\mathrm{CrB}{\mathrm{r}}_3/\mathrm{W}{\mathrm{S}}_2>\mathrm{Cr}{\mathrm{I}}_3\mathrm{WS}{\mathrm{e}}_2>\mathrm{Cr}{\mathrm{I}}_3/\mathrm{W}{\mathrm{S}}_2\right)$ on picosecond timescales. This behavior is governed by three key factors: (i) bandgap-dependent nonadiabatic coupling, where ${\mathrm{CrBr}}_3$ systems exhibit prolonged retention due to their larger energy gaps; (ii) spin-orbit coupling and electron-phonon coupling synergistically modulate spin-flip and transfer dynamics; and (iii) built-in electric fields that selectively accelerate or decelerate the interlayer charge transfer. These insights offer a comprehensive framework for understanding interfacial spin dynamics and provide design principles for tailoring spin lifetimes in two-dimensional heterostructure-based spintronic devices.

Close

PrevNext

View figure in article

• Electronic structure
• Spin dynamics
• Ultrafast magnetic effects
• Bilayer films
• Solid-solid interfaces
• Ab initio molecular dynamics
• Density functional calculations