Ferromagnetic barrier induced large enhancement of tunneling magnetoresistance in van der Waals perpendicular magnetic tunnel junctions.

van der Waals (vdW) intrinsic magnets are promising for miniaturization of devices beyond Moore's law for future energy efficient nanoelectronic devices and have been successfully used for constructing high performance vdW magnetic tunnel junctions (vdW MTJs). Here, using first principles calculations, we investigate the magnetic anisotropy, spin-dependent transport and tunneling magnetoresistance (TMR) effect of vdW MTJs formed by sandwiching a ferromagnetic (FM) monolayer CrI or non-magnetic monolayer ScI barrier between two vdW FM FeGeTe electrodes, respectively. It is found that two vdW MTJs possess strong perpendicular magnetic anisotropy. Moreover, due to no barrier for majority-spin transmission within half-metallic CrI barrier and the difference between majority- and minority-spin conduction channels of the FeGeTe electrode, a high TMR ratio of about 3100% is achieved in vdW MTJs based on the FeGeTe/CrI/FeGeTe vdW heterostructure. In contrast, a smaller TMR ratio of about 1200% is produced in vdW MTJs based on the FeGeTe/ScI/FeGeTe vdW heterostructure due to the strong suppression of ScI for majority-spin transmission in the case of the parallel state of magnetization of two FM electrodes. Our results provide a promising route for the design of vdW perpendicular MTJs with a high TMR ratio.