High transport spin polarization in the van der Waals ferromagnet Fe₄GeTe₂

The challenging task of scaling down the size of the power saving electronic devices can be accomplished by exploiting the spin degree of freedom of the conduction electrons in van der Waals (vdW) spintronic architectures built with 2D materials. One of the key components of such a device is a near-room temperature 2D ferromagnet with good metallicity that can generate a highly spin-polarized electronic transport current. However, most of the known 2D ferromagnets have either a very low-temperature ordering, poor conductivity, or low spin polarization. In this context, the FenGeTe2 (with n 3) family of ferromagnets stand out due to their near-room temperature ferromagnetism and good metallicity. We have performed spin-resolved Andreev reflection spectroscopy on Fe4GeTe2 (TCurie & SIM; 273 K) and demonstrated that the ferromagnet is capable of generating a very high transport spin polarization, exceeding 50%. This makes Fe4GeTe2 a strong candidate for application in all-vdW power -saving spintronic devices.