Electrical control of conductivity and magnetism in two-dimensional (2D) ferroelectric (FE) materials have attracted immense attention due to their fascinating properties and potential applications in designing field-effect transistors and high-density multistate data storage. Based on first-principles calculations and crystal field theory, we present an approach to obtain 2D intrinsic asymmetric multiferroics by replacing the In atom in the ferroelectric In2X3 monolayer (X = S, Se) with the Cr atom. Interestingly, it is found that the InCrX3 monolayers have two inequivalent polarized states, which are characterized by metal and semiconductor, respectively, which is related to the crystal field around Cr3+ ions. Thus, it provides a feasible way to realize electrical control of reversible metal–insulator transition induced by ferroelectric switching, indicating that the InCrX3 monolayers can be used as the channel materials in the FE memory technology. In addition, because of the existence of the Cr3+ ions, the InCrX3 monolayers also exhibit robust ferromagnetism with different Curie temperatures and magnetocrystalline anisotropy energies, which can provide a good platform for realizing the strong coupling between the magnetism and ferroelectricity. These interesting results provide a feasible way to design asymmetric FE materials with regulatable conductivity and magnetism that can enable a wide range of applications in nanodevices.

中文翻译：

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非对称多铁性 InCrX3 (X = S, Se) 单层中金属-绝缘体转变和磁性的电控制

二维（2D）铁电（FE）材料的电导率和磁性的电控制因其迷人的特性以及在设计场效应晶体管和高密度多态数据存储方面的潜在应用而引起了极大的关注。基于第一性原理计算和晶体场理论，我们提出了一种通过用 Cr 原子取代铁电 In2X3 单层（X = S，Se）中的 In 原子来获得二维本征不对称多铁性材料的方法。有趣的是，我们发现InCrX3单层具有两种不等价的极化态，分别具有金属和半导体的特征，这与Cr3+离子周围的晶体场有关。因此，它为实现铁电开关引起的可逆金属-绝缘体转变的电控制提供了一种可行的方法，表明InCrX3单层可以用作FE存储技术中的沟道材料。此外，由于Cr3+离子的存在，InCrX3单层还表现出不同居里温度和磁晶各向异性能量的强铁磁性，这可以为实现磁与铁电之间的强耦合提供良好的平台。这些有趣的结果为设计具有可调节电导率和磁性的不对称有限元材料提供了一种可行的方法，可以在纳米器件中实现广泛的应用。