  We have experimentally investigated the mechanism of the exchange bias in the
2D van der Waals (vdW) ferromagnets by means of the anomalous Hall effect (AHE)
together with the dynamical magnetization property. The temperature dependence
of the AC susceptibility with its frequency response indicates a glassy
transition of the magnetic property for the Te-rich FeGeTe vdW ferromagnet. We
also found that the irreversible temperature dependence in the anomalous Hall
voltage follows the Almeida-Thouless line. Moreover, the freezing temperature
of the spin-glass-like phase is found to correlate with the disappearance
temperature of the exchange bias. These important signatures suggest that the
emergence of magnetic exchange bias in the 2D van der Waals ferromagnets is
induced by the presence of the spin-glass-like state in FeGeTe. The
unprecedented insights gained from these findings shed light on the underlying
principles governing exchange bias in vdW ferromagnets, contributing to the
advancement of our understanding in this field.
