A device comprising a first magnetic layer (e.g., Co2MnSi Heusler alloy or a tetragonally distorted perpendicularly magnetized (PMA) Heusler alloy such as Mn3Ga, Mn3Ge, etc.) and a second magnetic layer (e.g., Co2MnSi Heusler alloy or a tetragonally distorted perpendicularly magnetized (PMA) Heusler alloy such as Mn3Ga, Mn3Ge, etc.), and a metal halide tunnel barrier in between the first and second magnetic layers, wherein the metal halide tunnel barrier (e.g., NaF, NaCl, NaBr, LiF, LiCl, and LiBr or their combination) is lattice matched within a predetermined limit (e.g. 5%) of both the first and second magnetic layers.