近年来，具有高铁电居里温度的铁电材料因是一种潜在的室温多铁材料而受到广泛的关注，但实验和理论上对无掺杂铁电薄膜中观察到的铁磁性来源都存在一定的分歧，实验上无法验证阳离子空位缺陷对磁性的影响，理论上没有考虑薄膜与衬底组成的界面以及阳离子和氧空位协同作用对薄膜磁性的影响。针对这些问题，本项目选择具有高铁电居里温度的A2Nb2O7型铌酸盐铁电材料Ca2Nb2O7为研究对象，利用脉冲激光沉积技术，通过阳离子缺陷靶材的制备和氧气压强的调节，在钙钛矿结构衬底上实现具有Ca/Nb/O单空位及Ca+O或Nb+O双空位缺陷Ca2Nb2O7薄膜的可控制备；磁性测量结合各种表征手段和第一性原理计算，探讨研究薄膜表面及界面处阳离子空位和氧空位缺陷单独作用及协同作用机制。本项目的开展有利于明确钙钛矿结构衬底上无掺杂铌酸盐薄膜磁性的来源，为A2Nb2O7型层状钙钛矿结构铌酸盐薄膜的磁性研究提供实验和理论依据。

Ferroelectric material with high Curie temperature is considered as potential multiferroics at room temperature, thus attracts considerable attention in recent years. However, the origin of ferromagnetism observed in undoped ferroelectric film is still unclear, the effect of cation vacancy on magnetism cannot be verified by experiment, the interface between film and substrate as well as the cooperative effect of cation and anion vacancy is unconsidered in theoretical calculation. To solve these problems, this project takes Ca2Nb2O7 as the object of research, which is a typical A2Nb2O7 niobate ferroelectric material with high Curie temperature. Controllable fabrication of Ca2Nb2O7 film on perovskite-type substrate with Ca/Nb/O single vacancy and Ca+O or Nb+O double vacancies is achieved through the preparation of ceramic target with cation defect and the adjustment of oxygen pressure during deposition using pulsed laser deposition technique. The effect of single vacancy and cooperative effect of Ca+O or Nb+O double vacancies are investigated by magnetic measurement in combination with related characterization and first principle calculations. This project will clarify the origin of magnetism in undoped niobate film on perovskite-type substrate, and provide experimental and theoretical reference for the study of d0 magnetism on A2Nb2O7-type niobate ferroelectric film with high Curie temperature.