Interface and transport properties of Fe/V/MgO/Fe and Fe/V/Fe/MgO/Fe magnetic tunneling junctions

Abstract

The interface and transport properties of Fe/V/MgO/Fe and Fe/V/Fe/MgO/Fe magnetic tunneling junctions are investigated by using density-functional theory and nonequilibrium Green's-function methods. Bader analysis reveals that the Fe layer at the interface with MgO loses a small amount of charge with respect to its bulk value, in contrast to a previous study ͓W. H. Butler, X.-G. Zhang, T. C. Schulthess, and J. M. MacLaren Phys, Rev. B 63, 054416 ͑2001͔͒. At the same time at the Fe/V interface a magnetic moment is induced on the V layer by proximity. Importantly, the direction of the magnetization of the first V monolayer immediately close to the MgO barrier oscillates with the total V-layer thickness and the relative stability of a particular magnetic configuration weakens as such a thickness is increased. These two aspects pose a challenge to the Fe/V/MgO/Fe device signal stability. A more intriguing situation is found for Fe/V/Fe/MgO/Fe junctions. Their transport properties depend sensitively on the thickness of the Fe layer intercalated between V and the MgO barrier. This is the result of resonances through quantum-well states of ⌬ 1 symmetry localized in the intercalated Fe layer. In particular, for some geometries we find a massive magnetoresistance obtained by simply switching the direction of the magnetization of the Fe interlayer, while keeping the direction of the electrodes fixed. This effect may be employed in the design of new spin valves with extremely high spin polarization but still relatively large current densities.

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

“…The same sensitive dependence of the mm of the interfacial layer is reported for Fe/V/MgO and Fe/Co heterostructures. 49,50 In the following, we provide a qualitative understanding of this finding. On the one hand, our calculations suggest hybridization of Fe 3d with O 2p states, where the electronic structure of both Fe and O resemble the state of FeO, which explains the formation of polarized oxygen-derived states usually found at the Fe-MgO interface.…”

Electron Correlation Enhances Orbital Polarization at a Ferromagnetic Metal/Insulator Interface: Depth-Resolved X-ray Magnetic Circular Dichroism and First-Principles Study

“…It was theoretically predicted that the Fe spin and orbital magnetic moments increase when interfaced with MgO. − Experimentally, Miyokawa et al and Sicot et al observed such enhancements in a 1–2-monolayer (ML) thick Fe sandwiched between MgO and Co layers by performing X-ray magnetic circular dichroism (XMCD) measurements, , although the authors recognized that the Co underlayer most likely affected the magnetic properties of such a thin Fe layer. Jal et al showed that the magnetic moments increased by 24% in a 2–3-ML thick Fe next to an interface in an MgO/Fe (12 nm)/MgO heterostructure .…”

Taming the resistive switching in Fe/MgO/V/Fe magnetic tunnel junctions: An ab initio study

“…To compute the conductance, we have used 400×400 k points in the two dimensional Brillouin zone as used in Ref. [22]. This high mesh is required for the good convergence of the conductance.…”

“…The mem-ristor model [21] was shown to be good for explaining the hysteresis-like I-V characteristics. The conductance of Fe/MgO/V/Fe was shown to oscillate with increasing the number of vanadium layers [22]. Another reason for including vanadium at the Fe/MgO interface, lies in the higher oxygen affinity of this element compared to iron.…”