Robust Vertical Exchange Bias Modulates Spin Decoherence in 0D Core–Shell Nanoparticles

While recent advancements in spin manipulation have utilized
topological
insulators and non-collinear antiferromagnets confined to two-dimensional
films, dimensional limitations have hindered the realization of truly
freestanding spin-dependent quantum nanodevices (nm3).
Here, we exploit a robust vertical exchange bias confined within core–shell
FePt@MnO nanoparticles (D ∼ 9 nm) to control
the spin decoherence time of Fe and Mn magnetic atoms. The magnitude
(approximately 17% of interfacial spins are fully pinned) and robustness
(the pinned spins remain stable even under a negative field of −5
T) of this anomalous exchange bias arise from a coherent interface
where strain-induced lattice distortion displaces Mn cations by ångström-scale
distances from their equilibrium positions, aligning them with Fe
cations. This interfacial coherence enhances interfacial spin–spin
exchange couplingmanifested as the anomalous exchange-bias
effectwhich directly modulates spin decoherence dynamics:
τ2 for Mn2+ spins shortens by 9.8% (108.3
ps → 98.5 ps), while Fe spins exhibit a concomitant τ2 enhancement. This work establishes a direct link between
spin decoherence time and the exchange-bias effect, offering a pathway
for the coherent engineering of quantum nanomaterials.