npj Computational Materials

Ferromagnetism and ferroelectricity in a superlattice of antiferromagnetic perovskite oxides without ferroelectric polarization

Paresh C. Rout, Avijeet Ray & Udo Schwingenschlögl

npj Computational Materials 9: 165 (2023).

doi.org/10.1038/s41524-023-01112-6

Published online: 01 September, 2023

编辑概述

SrCrO₃/YCrO₃超晶格：铁磁性和铁电性

过渡金属钙钛矿（ABO₃）的异质结构为研究关联电子现象提供了肥沃的土壤，并为利用量子效应获得新的功能器件提供了一条很有前景的途径。SrCrO₃是一种金属d²钙钛矿，具有非极性四方空间群P4/mmm，在Néel 温度以下呈现C型反铁磁（C-AFM）结构。YCrO₃是一种半导体d³钙钛矿，具有非极性正交空间群Pbnm，在Néel 温度以下呈现G-AFM结构。研究SrCrO₃/YCrO₃超晶格的电子和磁性特性非常有趣，因为这两种材料都没有磁化和铁电极化，而它们的电子和磁性特性可以通过应变工程来控制。在本工作中，来自沙特阿拉伯阿卜杜拉国王科技大学物理科学与工程系的Udo Schwingenschlögl教授课题组，研究了SrCrO₃/YCrO₃超晶格的多铁性质对外延应变的依赖性。作者通过第一性原理计算，预测了SrCrO₃/YCrO₃超晶格大的杂化非本征铁电极化。结果显示，即使在同时缺乏磁性和铁电性的钙钛矿氧化物中，超晶格的形成也能诱导多铁性。在无应变和施加压应变的情况下，SrCrO₃/YCrO₃超晶格保持A-AFM序。而在+1%拉伸应变作用下，该超晶格转变为铁磁相。此外，棋盘电荷排序导致了具有窄间接带隙的绝缘体。这种铁磁相中电荷序驱动的p型半导体态是自旋电子学中一种罕见而有趣的特性。这种杂化非本征的铁电极化来源于Sr²⁺和Y³⁺阳离子的反极位移（可由应变控制）之间的较大差异，其位移差异大小接近于传统的铁电氧化物，如钛酸钡。尽管单个化合物没有铁电性，但通过大的铁电极化可以实现磁态。该研究指出，大磁化强度与大铁电极化的结合产生了强大的多铁性，这使多态存储器的应用成为可能。

Editorial Summary

SrCrO₃/YCrO₃ superlattice: Ferromagnetism and ferroelectricity

Heterostructures of transition metal perovskites (ABO₃) provide a fertile ground to study emergent phenomena of correlated electrons and a promising route to new functional devices using quantum effects. SrCrO₃ is a metallic d² perovskite with the nonpolar tetragonal space group P4/mmm and C-type antiferromagnetic (C-AFM) ordering below the Néel temperature. YCrO₃ is a semiconducting d³ perovskite with the nonpolar orthorhombic space group Pbnm, G-AFM ordering below the Néel temperature. It is particularly interesting to explore the electronic and magnetic properties of the SrCrO₃/YCrO₃ superlattice, as both component materials lack magnetization and ferroelectric polarization while their electronic and magnetic properties can be controlled by strain engineering. In this work, a group led by Prof. Udo Schwingenschlögl from the Physical Science and Engineering Division, King Abdullah University of Science and Technology, Saudi Arabia, studied the dependence of the multiferroic properties of the SrCrO₃/YCrO₃ superlattice under epitaxial strain. The authors predicted by first-principles calculations large hybrid-improper ferroelectric polarization for the superlattice composed of the perovskites SrCrO₃ and YCrO₃. They demonstrated that the formation of a superlattice is able to induce multiferroism even in perovskite oxides lacking both magnetism and ferroelectricity individually. The SrCrO₃/YCrO₃ superlattice adopts an A-AFM ordering without strain and under compression, while it becomes FM with a magnetization of 5 μ_B per formula unit at +1% strain. In addition, it was found that the checkerboard charge ordering results in a band insulator with a narrow indirect bandgap. The charge-order-driven p-type semiconducting state of the ferromagnetic phase is a rare property and interesting for spintronics. The hybrid-improper ferroelectric polarization is due to a large difference between the antipolar displacements of the Sr²⁺ and Y³⁺ cations (which can be controlled by strain) and its magnitude approaches that of conventional ferroelectric oxides such as BaTiO₃. Magnetic states can be realized with large ferroelectric polarization despite the fact that the individual compounds show no ferroelectricity. The work suggest that the combination of large magnetization with large ferroelectric polarization gives rise to robust multiferroism, enabling multistate memory applications.