First-principles study of enhancement of perpendicular magnetic anisotropy obtained by inserting an ultrathin LiF layer at an Fe/MgO interface.

Perpendicular magnetic anisotropy (PMA) is a key property of magnetoresistive random access memory (MRAM). To increase areal density of MRAM it is important to find a way to enhance the PMA. Recently a strong enhancement of the PMA by inserting an ultrathin LiF layer at an Fe/MgO interface was reported [T. Nozaki et al., NPG Asia Materials (2022) 14: 5]. To understand the origin of the observed enhancement of the PMA we perform first-principles calculations of magnetocrystalline anisotropy energy (MAE) of the following four kind of multilayer structures: Fe/MgO, Fe/LiF/MgO, Fe/FeO/MgO, and Fe/FeF/LiF/MgO. We find that the MAEs of the Fe/LiF/MgO and the Fe/FeF/LiF/MgO structures are almost the same as that of the Fe/MgO structure, while the MAE of the Fe/FeO/MgO structure is less than a half of that of the Fe/MgO structure. The results show that the major origin of the enhancement of the PMA obtained by inserting an ultrathin LiF layer at an Fe/MgO interface is the suppression of the mixing of Fe and O atoms at the interface. We also find that the in-plane Fe–F coupling gives a positive contribution to the MAE while the in-plane Fe–O coupling gives a negative contribution. The results are useful for designing of high-PMA materials. • Perpendicular magnetic anisotropy (PMA) is a key property of MRAM. • The enhancement of PMA by inserting a LiF layer at an Fe/MgO interface is studied. • The origin of the enhancement is the suppression of mixing of Fe and O atoms. [ABSTRACT FROM AUTHOR]