Giant Tunneling Electroresistance Effect Driven by an Electrically Controlled Spin Valve at a Complex Oxide Interface

A giant tunneling electroresistance effect may be achieved in a ferroelectric tunnel junction by exploiting the magnetoelectric effect at the interface between the ferroelectric barrier and a magnetic ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ electrode. Using first-principles density-functional theory we demonstrate that a few magnetic monolayers of ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ near the interface act, in response to ferroelectric polarization reversal, as an atomic-scale spin valve by filtering spin-dependent current. This produces more than an order of magnitude change in conductance, and thus constitutes a giant resistive switching effect.

Figure 1

Schematic side view of the layer-by-layer atomic positions and magnetoelectric state of the system. The ferroelectric polarization in the ${\mathrm{BaTiO}}_3$ is indicated by large arrows and the magnetic moment on the Mn sites is indicated by the small arrows. (a) For polarization to the right the Mn magnetic moments are ferromagnetically ordered throughout the right electrode. (b) Configuration with polarization to the left where Mn magnetic moments are assumed to be ferromagnetically ordered everywhere. (c) The ground state magnetic configuration for polarization to the left.

Figure 2

(a) Profile of the relative metal-oxygen ($M\mathrm{\text{−}}\mathrm{O}$) displacements in each atomic layer for two polarization states. The solid symbols are $B\mathrm{\text{−}}{\mathrm{O}}_2$ displacements ($B=\mathrm{Mn}$ or Ti) and the open symbols are $A\mathrm{\text{−}}\mathrm{O}$ displacements ($A={\mathrm{La}}_{1-x}{\mathrm{Sr}}_x$ or Ba). Squares, circles, and triangles correspond to the magnetoelectric states depicted in Figs. 1a, 1b, 1c, respectively. (b) Macroscopic and planar averaged electrostatic potential profile of the junction. Dotted, solid, and dashed curves correspond to the magnetoelectric states depicted in Figs. 1a, 1b, 1c, respectively.

Figure 3

(a)–(c) The ${\mathbf{k}}_{\parallel }$-resolved distribution of the transmission in the 2D Brillouin zone for different magnetoelectric states depicted in Figs. 1a, 1b, 1c, respectively. The integrated total conductance $G$ [see Eq. (1)] is given in the lower-left corner of each plot (in units of ${10}^{-6}{e}^2/h$). Note that the color scale is logarithmic and the gray areas correspond to zero transmission.

Figure 4

(a)–(c) Local density of states (LDOS) of the first, second, and third unit cells of ${\mathrm{La}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{MnO}}_3$, respectively, near the interface for polarization pointing to the right. The left (right) panels are for spins parallel (antiparallel) to the bulk magnetization. (d)–(f) The same as in (a)–(c) except for ferroelectric polarization to the left.