Ab initio investigation of structure, magnetism and ferroelectricity and their interplay in multiferroic bulk materials and films

在过去的几年里，磁电子学和自旋电子学已经成为一个非常活跃和有前途的探索性研究领域，并作为一种新的纳米电子学范式发展起来，其中除了电荷之外，电子的自旋或材料的磁化也被用作信息存储或处理的新自由度。相关的新的多功能金属氧化物隧道结的未来设备，如4位甚至8位存储器需要使用多铁性材料，它的双磁性和电极化的同时。重点讨论了由铁磁引线和铁电氧化物或多铁氧化物作为势垒组成的多铁性隧道结。理论上理解这样的结和材料需要计算机模拟的现象有关的结构，化学和电子的复杂性，在散装，薄膜和结。我们使用密度泛函理论来探索多铁性块体材料和薄膜的电子结构对化学组成、结构弛豫、维数和温度的依赖性，目标是预测具有改进功能的新型多铁性材料。

In the past years, magnetoelectronics and spintronics have emerged as a very activeand promising field of exploratory research and developed as a new paradigm ofnanoelectronics where, besides the charge, also the spin of an electron or the magnetizationof a material is used as a new degree of freedom for information storage orprocessing. Relevant novel multifunctional metal-oxide tunnel junctions for future deviceslike 4- or even 8-bit memory require the use of multiferroic materials which exhibita magnetic and an electric polarization simultaneously. Emphasis is put on multiferroictunnel junctions consisting of ferromagnetic leads and ferroelectric oxides or multiferroicoxides as barriers. A theoretical understanding of such junctions and materials requirescomputer simulations of phenomena related to their structural, chemical and electroniccomplexity, in bulk, films and junctions. We use density-functional theory to explore thedependence of the electronic structure of multiferroic bulk materials and films onchemical composition, structural relaxation, dimensionality, and temperature, with thegoal of predicting novel multiferroic materials with improved functionality.