Van der Waals heterostructures with two-dimensional magnets offer a magnetic junction with an atomically sharp and clean interface. This attribute ensures that the magnetic layers maintain their intrinsic spin-polarized electronic states and spin-flipping scattering processes at a minimum level, a trait that can expand spintronic device functionalities. Here, using a van der Waals assembly of ferromagnetic Fe3GeTe2 with non-magnetic hexagonal boron nitride and WSe2 layers, we demonstrate electrically tunable, highly transparent spin injection and detection across the van der Waals interfaces. By varying an electrical bias, the net spin polarization of the injected carriers can be modulated and reversed in polarity, which leads to sign changes of the tunnelling magnetoresistance. We attribute the spin polarization reversals to sizable contributions from high-energy localized spin states in the metallic ferromagnet, so far inaccessible in conventional magnetic junctions. Such tunability of the spin-valve operations opens a promising route for the electronic control of next-generation low-dimensional spintronic device applications.

We investigate the atomic structure of (n = 9-14) clusters using the first-principles pseudopotential method within the local-density-functional approximation (LDA). The equilibrium geometries of small clusters with tend to be capped prismatic structures. For n = 13, we find a surface-like metallic compact structure which is derived from a capped icosahedron and competes with a stable trigonal prism, while this structure is the most stable for n = 14. These results are compatible with the observed stability of and , as compared to clusters with nearby values of n, against chemical reactions with simple molecules. The effect of electron-electron correlations on the energetics of isomers with n = 13 is examined through variational quantum Monte Carlo calculations, and the LDA energy ordering remains unchanged, consistently with previous diffusion quantum Monte Carlo calculations.