Are insulating LiF barriers relevant for spin-polarized tunnelling applications? Insights from first-principles calculations

Abstract

Structural, electronic and magnetic properties of Fe/LiF (0 0 1) interfaces and spin-polarized transport properties of Fe/LiF/Fe (0 0 1) heterostructures are studied by means of self-consistent atomistic first-principles calculations. Total energy calculations performed for various interfacial geometries show that the Fe/LiF (0 0 1) interface with Fe atoms located above anionic sites is the most stable. F–Fe and Li–Fe substitutional intermixings at Fe/LiF (0 0 1) interfaces are not energetically favourable, but F accumulation in the interstitial void spaces at Fe/LiF (0 0 1) interfaces is possible. The magnetism of interfacial Fe atoms is robust. The majority-spin ferromagnetic state conductances decay rapidly with respect to the barrier thickness, while the minority-spin ones have very large contributions at specific hot spots and play a major role in the transport properties. Depending on the interfacial geometry, tunnelling magnetoresistance ratios ranging from 460%–2400% are evidenced. Interfacial interdiffusion can affect the transport properties. The exchange coupling between Fe electrodes through LiF barriers is negligible.