Ferroelectric control of spin-transfer torque in multiferroic tunnel junctions

Abstract

Based on model calculations we predict electric-field control of the spin transfer torque (STT) in magnetic tunnel junctions with ferroelectric barriers. We demonstrate that the bias dependence of the in-plane, T , and out-of-plane, T ⊥ , components of the STT can be dramatically modified by the ferroelectric polarization. In particular, the magnitude of the STT can be enhanced or suppressed by switching the polarization direction and in some cases the sign of STT can be toggled. The underlying mechanism is the combination of polarization-induced symmetry breaking and the interplay of the bias-induced and polarization-induced spin-dependent screening giving rise to a rich behavior of the electrostatic potential energy profile. These properties could lead to enhanced switching efficiency in STT-based devices and open a new avenue for applications of multiferroic devices.

Electric Field Control of the Resistance of Multiferroic Tunnel Junctions with Magnetoelectric Antiferromagnetic Barriers

“…We calculate the tunneling current for the different configurations of the order parameters in the MFTJ using the fully non-collinear non-equilibrium Green's function (NEGF) formalism developed earlier to investigate the transport properties of MFTJs with FE barriers [30,31]. The electronic structure of the junction is modeled by a single-orbital tight-binding Hamiltonian on a simple cubic lattice in the standard (001) orientation.…”

“…For the electrode material we chose Fe as a typical FM metal. Correspondingly the spin-dependent onsite energies for majority and minority spin channels are set to ↑ = 2.6 eV and ↓ = 4.6 eV [31]. In the barrier we aim at capturing qualitatively the essential features of the electronic structure in AFM insulators such as chromia and BFO [32,33].…”

“…The electrostatic potential across the MFTJ is determined in the presence of finite bias and FE polarization by solving Poisson's equation with the following boundary conditions [6,30,31,34]: (i) Constant chemical potentials in the right and left electrodes which are shifted by the applied bias V as eV = µ R − µ L . (ii) Thomas-Fermi screening in the electrodes, where the screening lengths λ L/R are determined from the electronic structure.…”

Dual Control of Giant Field-like Spin Torque in Spin Filter Tunnel Junctions

“…The insulator in conventional FM/I/FM MTJs plays only a passive role in the spin-polarized transport. The evolution beyond passive components has broadened the quest for multifunctional spintronic devices consisting of either ferroelectric 14 15 16 17 18 19 or spin-filter (SF) barriers 20 21 22 23 . The latter exploits the separation of the barrier heights, φ σ , of the two spin channels, 2Δ ≡ φ ↑ − φ ↓ , which can be in turn tuned via an external magnetic field 20 23 .…”

Electric-field tunable spin diode FMR in patterned PMN-PT/NiFe structures

“…6 Application of multiferroic materials can additionally lead to the design of new electronic devices in which both the electron spin and charge are affected by an external electric field. Voltage control of magnetic anisotropy (VCMA) in multiferroics can be realized by strain transfer from a ferroelectric or piezoelectric layer to a ferromagnetic film, as the deformation of the ferromagnet changes the magnetoelastic anisotropy via inverse magnetostriction.…”