Giant multiferroic effects in topological GeTe-Sb₂Te₃superlattices

Abstract

Multiferroics, materials in which both magnetic and electric fields can induce each other, resulting in a magnetoelectric response, have been attracting increasing attention, although the induced magnetic susceptibility and dielectric constant are usually small and have typically been reported for low temperatures. The magnetoelectric response usually depends on d-electrons of transition metals. Here we report that in [(GeTe)2(Sb2Te3)l]m superlattice films (where l and m are integers) with topological phase transition, strong magnetoelectric response may be induced at temperatures above room temperature when the external fields are applied normal to the film surface. By ab initio computer simulations, it is revealed that the multiferroic properties are induced due to the breaking of spatial inversion symmetry when the p-electrons of Ge atoms change their bonding geometry from octahedral to tetrahedral. Finally, we demonstrate the existence in such structures of spin memory, which paves the way for a future hybrid device combining nonvolatile phase-change memory and magnetic spin memory.

Impact of Stoichiometry on the Structure of van der Waals Layered GeTe/Sb2Te3 Superlattices Used in Interfacial Phase‐Change Memory (iPCM) Devices

“…By contrast, in a PCM cell based on a GST alloy, a high RESET current is needed to melt the material prior to amorphization. iPCMs open numerous opportunities for multilevel storage, hybrid devices combining resistive and magnetic memories, logic gate devices, and also devices for THz pulse detection . Incorporation of SLs in iPCM devices by using ULSI microelectronics technology has been demonstrated for large density memory arrays…”

A two-step process for growth of highly oriented Sb2Te3 using sputtering

“…11 Furthermore, several superlattice structures including GeTe/Sb 2 Te 3 have been theoretically predicted to exhibit unusual properties forming topological insulators or Dirac semimetals, leading to the experimental confirmation of unusual magnetic properties despite the lack of magnetic elements. [12][13][14][15] The most widely used techniques to fabricate 2D chalcogenides are exfoliation from a bulk single crystal, chemical vapor deposition (CVD), and molecular beam epitaxy (MBE). [16][17][18][19][20][21] However, the area of films that can be fabricated by exfoliation is limited and sample sizes are not uniform.…”

Local atomic arrangements and lattice distortions in layered Ge-Sb-Te crystal structures

“…Interfacial PCMs (iPCMs)9 or chalcogenide superlattices consisting of Sb 2 Te 3 and GeTe multilayers are a promising candidate for data storage devices with reduced energy consumption since reversible transition between SET and RESET states is assumed to be constrained by motion of atoms in 1D instead of 3D as in the case of conventional PCM devices. Thus, the switching mechanism of iPCMs is determined by the local atomic arrangement in distinct layers10111213, which also defines the electronic properties of the materials14. In particular, theoretical simulations showed that iPCMs can be a 3-D topological insulator15 or a Dirac semimetal11.…”