Role of an interfacial FeO layer in the electric-field-driven switching of magnetocrystalline anisotropy at the Fe/MgO interface

Abstract

The electric-field-induced switching of magnetocrystalline anisotropy ͑MCA͒ between in-plane and out-ofplane orientations is investigated by first-principles calculations for the prototypical Fe on MgO͑001͒ system. Our results predict that an ideal abrupt Fe/MgO interface gives rise to a large out-of-plane MCA due to weak Fe-O hybridization at the interface, but the MCA switching by an applied electric field is found to be difficult to achieve. Instead, the existence of an interfacial FeO layer plays a key role in demonstrating the MCA switching that accompanies an electric-field-induced displacement of Fe atoms on the interfacial FeO layer.Controlling magnetic properties by means of applied electric field ͑E field͒ is a key challenge in materials physics. Materials being studied include magnetoelectric multiferroics 1-4 and magnetic semiconductors. 5-7 Even in itinerant thin films, magnetic properties such as the magnetocrystalline anisotropy ͑MCA͒ are modified by application of a voltage; 8 there is general consensus that modification of the surface d-electron charge/spin density induced by the E field contributes to the effect. [9][10][11][12] Magnetic metal-oxide junctions are seen as an important avenue toward ultrahigh density and nonvolatile electronics 13,14 needed for information processing and storage technologies. Recent experiments have reported that the perpendicular MCA energy is significantly reduced by an applied voltage in Au/Fe/MgO junctions, 15 i.e., at ultrathin Fe/MgO interfaces. Moreover, the direct switching from out of plane to in plane has been achieved in Au/ Fe 0.8 Co 0.2 / MgO. 16 Such E-field-driven MCA switching offers a pathway to control magnetism at the nanoscale with ultralow-energy power consumption compared to traditional switching using magnetic fields. Despite its importance, an understanding of the underlying physics and mechanism of the E-field-driven MCA modification in metal-oxide interfaces is still lacking due to the structural and electronic complexity of the interfaces, thus, hindering the search for other promising metal-oxide interface candidates.Here, we present a mechanism for the E-field-driven MCA modification at the Fe/MgO interface, based on fullpotential linearized augmented plane-wave ͑FLAPW͒ calculations. 17,18 These calculations predict that an ideal abrupt Fe/MgO interface gives rise to a large out-of-plane MCA due to weak Fe-O hybridization at the interface, and that the MCA modification is caused by changes in the d-band structure at the Fermi level ͑E F ͒ when an E field is introduced. However, the MCA switching by an applied E field is found to be difficult to achieve. Instead, the existence of an interfacial FeO x layer between the metallic Fe layer and the MgO substrate plays a key role in facilitating the MCA switching, which accompanies an E-field-induced displacement of the Fe atoms in the interfacial FeO layer.Calculations were performed using the FLAPW method which treats a single slab geometry 17,18 that allows a natural way to include an exte...

Ferroelectric Control of Magnetocrystalline Anisotropy at Cobalt/Poly(vinylidene fluoride) Interfaces

“…13 Theoretically, the electric field effect on the MCA was investigated for various free-standing magnetic metal films 10,14-17 and Fe/MgO interfaces. 18,19 Very recently, electrically induced bistable magnetization switching was realized in MgO-based magnetic tunnel junctions at room temperature, 20,21 demonstrating the capabilities of this approach for magnetic data storage applications. 22 Alternatively, the interface magnetic anisotropy (and hence the magnetization orientation) may be tailored electronically by the ferroelectric polarization of an adjacent ferroelectric film.…”

Extremely large perpendicular magnetic anisotropy of an Fe(001) surface capped by5dtransition metal monolayers: A density functional study

“…A few theoretical groups also addressed Fe/MgO and FeCo/MgO interfaces and have argued that the PMCA of the Fe(001) film is enhanced by the hybridization of Fe 3d orbitals with O p z . 6,7 Nevertheless, recent experiments on TMs/FeCoB/MgO revealed evidence that the role of 5d or 4d orbitals is more decisive; in other words, that the 5d (4d) TMs/CoFeB interface is the origin of the observed PMCA. 8,9 On the other hand, the magnetism in multilayers of 4d and 5d TMs grown on body-centered cubic (bcc) Fe substrate has been a long-standing subject of both experiment [10][11][12][13][14][15] and theory.…”

Electric-field control of domain wall nucleation and pinning in a metallic ferromagnet

“…As the majority of these materials loses their ferromagnetic properties at room temperature the recent discovery of an important ME effect at room temperature in conventional ferromagnetic metals 3-8 has attracted much attention. Despite the limited penetration depth of an E-field in metals, the charge induced at the metal/dielectric interface on the topmost atomic layers is sufficient to modify the surface magnetic anisotropy energy (MAE) by a non negligible amount in ultrathin ferromagnetic layers as suggested by electronic structure calculations [9][10][11] . This has a particular impact in systems where the different anisotropy contributions almost cancel each other out, resulting in a large relative variation of the total effective MAE when the surface contribution is modified with the voltage [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] .…”