Interfacial geometry dependence of the iron magnetic moment: The case of MgO/Fe/MgO

Abstract

The prediction and experimental demonstration of a very large magnetoresistance in Fe/MgO/Fe tunnel junctions have led to intense study of related systems in the last decade. In the present paper, we concentrate on the role of interface coordination, Fe thickness, and magnetization in the MgO/Fe/MgO mirror. By first-principles analysis, it is shown that the iron magnetic moment can rise up to 4 μ B , accounting for observed deviation of the Fe atoms in the vicinity of MgO interfaces. The origin is attributed to site preference predicted by our calculations, namely, that, unlike the case of Fe atoms in the monolayer range sitting just above the oxygen atoms of the MgO(001) substrate, the charge transfer induced by the O p-d Fe interaction leads to a structural distortion that stabilizes the Mg at the very first deposition stages of the capping layer, facing Fe sites.

Interface Fe magnetic moment enhancement in MgO/Fe/MgO trilayers

“…First, the absence of an out-of-plane magnetization component is expected for a Fe thickness of 12 nm. 34 Second, the increase of the magnetic moment in the 2-3 ML near both MgO interfaces confirms the theoretical predictions 19,20 and is in good agreement with experimental work published for samples of only a few Fe monolayer thicknesses. 21 Indeed, theoretically, Li and Freeman demonstrated that an enhancement of 30% of the magnetic moment was expected for a 2ML Fe thick film on MgO.…”

“…17,18 For such Fe/MgO interfaces, the hybridization between Fe and MgO has been theoretically predicted to result in a significant enhancement of the interfacial Fe magnetic moment similar to the one expected for freestanding Fe monolayers. 19,20 Experimentally these predictions have been corroborated by probing the thickness dependent total magnetic moment of 1-6 ML thick Fe films on MgO yielding indirect evidence for interfacial moment enhancement in actual device structures 16,21,22 or other substrates with similarly strong electronic hybridization. 23 There has been no experimental study probing the depth dependence of the Fe magnetic moment within a single MgO/Fe/MgO heterostructure.…”

First-principles study of the adsorption of MgO molecules on a clean Fe(001) surface

“…The equilibrium structures of the MgO layers on Fe(001) were optimized with an a priori assumption that the oxygen preferably adsorbs at the on-top sites. However, the calculation by Beltrán et al 35 suggested that under low MgO coverage, Fe binds to Mg rather than to O.…”

Enhanced magneto-optical Kerr effect at Fe/insulator interfaces

“…Instead, it focuses on spin-orbit interactions, which can be enhanced by our method, while they have been ignored in previous applications of plasmonic or photonic effects. We were motivated by the discovery of large magnetic anisotropies in ultrathin Fe/MgO films [43][44][45][46][47] . The Fe/MgO interface is used in a wide range of devices, and enhanced spin-orbit interactions are expected because of the large magnetic anisotropy.…”