Anatomy of Magnetic Anisotropy and Voltage-Controlled Magnetic Anisotropy in Metal Oxide Heterostructure from First Principles

Abstract

Voltage control of magnetic anisotropy (VCMA) is one of the promising approaches for magnetoelectric control of magnetic tunnel junction (MTJ). Here, we systematically calculated the magnetic anisotropy (MA) and the VCMA energies in the well-known MTJ structure consisting of Fe/MgO interface with Cr buffer layer. In this calculation, we investigated an alloying between Fe and Cr and a strain effect. We used a spin density functional approach which includes both contributions from magnetocrystalline anisotropy energy (MCAE) originating from spin–orbit coupling and shape magnetic anisotropy energy from spin dipole–dipole interaction. In the present approach, the MCAE part, in addition to a common scheme of total energy, was evaluated using a grand canonical force theorem scheme. In the latter scheme, atom-resolved and k-resolved analyses for MA and VCMA can be performed. At first, we found that, as the alloying is introduced, the perpendicular MCAE increases by a factor of two. Next, as the strain is introduced, we found that the MCAE increases with increasing compressive strain with the maximum value of 2.2 mJ/m2. For the VCMA coefficient, as the compressive strain increases, the sign becomes negative and the absolute value becomes enhanced to the number of 170 fJ/Vm. By using the atom-resolved and k-resolved analyses, we clarified that these enhancements of MCAE and VCMA mainly originates from the Fe interface with MgO (Fe1) and are located at certain lines in the two dimensional Brillouin zone. The findings on MCAE and VCMA are fully explained by the spin-orbit couplings between the certain d-orbital states in the second-order perturbation theory.

Voltage-controlled magnetic anisotropy-based spintronic devices for magnetic memory applications: Challenges and perspectives

“…( 6). Interested readers can explore several insightful review articles by Nozaki et al in 2019, 114 Pardede et al in 2020, 123 and Shao and Khalili Amiri in 2023. 124 They primarily focused on the mechanisms and applications of the VCMA.…”

Ultralow Electric Current-Assisted Magnetization Switching due to Thermally Engineered Magnetic Anisotropy

“…The remarkable progress in this field, particularly the effective electric field modulation of magnetic anisotropy, is of great technical significance for realizing fast and low-power magnetized switches. , Approaches for the traditional electrical manipulation of magnetic anisotropy include utilizing magnetoelectric heterostructures, field-effect devices with solid or electrolyte gates, and magnetoionic systems, all of which require additional fabrication and modulation processes as well as a complicated device architecture. , For example, the magnetoelectric heterostructures need an expensive single-crystal substrate, additional electrode design, and control circuit, which bring many difficulties to device design and preparation and are not conducive to device integration. Recently, a new mechanism of current regulation of magnetism based on thermally induced anisotropy reorientation has received considerable research interest. , Thermally assisted magnetization switching in STT-based spintronics has been demonstrated with maximum torque efficiency due to the heating-induced orthogonal arrangement of injected spin polarization and free layer magnetization …”

“…8−11 The remarkable progress in this field, particularly the effective electric field modulation of magnetic anisotropy, is of great technical significance for realizing fast and low-power magnetized switches. 12,13 Approaches for the traditional electrical manipulation of magnetic anisotropy include utilizing magnetoelectric heterostructures, field-effect devices with solid or electrolyte gates, and magnetoionic systems, all of which require additional fabrication and modulation processes as well as a complicated device architecture. 14,15 For example, the magnetoelectric heterostructures need an expensive singlecrystal substrate, additional electrode design, and control circuit, which bring many difficulties to device design and preparation and are not conducive to device integration.…”