Gallium Iron room temperature Magnetoelectric Oxides

磁电（ME）材料，在其磁性和电性能之间表现出耦合，允许通过电场控制材料的磁化强度。这为一种具有高耐用性、低存取时间和低功耗的新型非易失性存储器开辟了前景：磁电存储器（MERAMs）。不幸的是，呈现ME耦合的材料很少。那些在室温下表现出这种效应并具有非零磁化强度的材料，对于实际应用的发展至关重要，甚至更少。我们建议从磁电的角度研究一种有前途但仍然未知的材料的可能性，特别是在薄膜中：Ga2-xFexO3 （GFO）。这种材料是热释电的，铁磁性的，并且具有单相材料中观察到的最高ME耦合之一。这是第一个观察到同时呈现强ME耦合和由此产生的磁化的材料。当x=1.4时，它的居里温度高于室温（370 K）。然而，其电气和ME特性的起源仍不清楚。直到最近，还没有足够高结晶质量的这种材料的薄膜能够被制造出来。这实际上扼杀了它在电子设备中的潜在应用。本项目拟利用其中一个合作伙伴最近获得的能力，沉积高质量的GFO薄膜。其目标是完成GFO磁电的完整理论和实验研究。理论部分将包括第一性原理计算，旨在确定GFO中ME效应的起源，以期找到增加它的方法。在理论部分的指导下，将考虑不同掺杂的GFO结构。通过将理论部分的预测结果与纯GFO薄膜和掺杂GFO薄膜的ME效应实验表征进行对比，事后评估理论部分的一致性。

Magnetoelectric (ME) materials, presenting a coupling between their magnetic and electric properties, allow the control of the magnetization of a material through an electric field. This opens perspectives towards a new type of non volatile memory with high endurance, low access time and low power consumption: magnetoelectric memories (MERAMs). Unfortunately, materials presenting a ME coupling are scarce. Those presenting this effect at room temperature and having a non zero magnetization, essential for the real development of the applications, are even scarcer.We propose to study the possibilities in terms of magnetoelectricity of a promising but still rather unknown material, especially in thin films: Ga2-xFexO3 (GFO). This material is pyroelectric, ferrimagnetic, and has one of the highest ME couplings observed for a single-phased material. It’s the first material observed to simultaneously present a strong ME coupling and a resulting magnetization. Its Curie temperature is above room temperature (370 K) for x=1.4. The origin of its electric and ME properties is however still unclear. Until recently, no sufficiently high crystalline quality thin films of this material could be made. This de facto annihilated its potential applications in electronic devices.This project proposes to take advantage of the ability recently acquired by one of the partners to deposit high quality GFO thin films. Its goal is to perform a complete theoretical and experimental study of GFO magnetoelectricity. The theoretical part will consist in first principles calculations aiming at determining the origin of the ME effect in GFO, with a view to find ways to increase it. Different dopings of the GFO structure will be considered, guided by the theoretical part. Consistency of the theoretical part will be evaluated a posteriori through comparison of its predictions with the ME effect experimental characterization of pure and doped GFO thin films.