In order to break the contradictory requirements of the outer shell electronic structure for multiferroism in oxide perovskites, multiferroic fluorides were selected to be studied, in which the ferroelectricity and ferromagnetism may both come from the same magnetic ions. Pure phase Ba₅Fe₃F_19−δ powders were prepared by solid state reaction. Energy dispersive X-ray spectroscopy results indicate the deficiency of Fe. The mixed valence states of Fe³⁺ and Fe²⁺ are confirmed by X-ray photoelectron spectroscopy. The observation of amplitude and phase hysteresis loops measured by piezoresponse force microscopy indicates the ferroelectricity in Ba₅Fe₃F_19−δ. The temperature dependent magnetization curves show a continuous increase with decreasing temperature, without clear phase transition. However, the temperature dependent inverse magnetic susceptibility (χ) follows the Curie–Weiss law above 150 K with Curie–Weiss temperature of −55 K, suggesting predominantly antiferromagnetic interactions between the Fe ions. The χT decreases with the temperature decreasing from 300 K, indicating the onset of weak antiferromagnetic interaction from temperature above 300 K. No hysteresis loop was observed for the magnetic dependent magnetization curves down to 5 K, indicating the lacking of long-range ordering. A peak was observed in the temperature dependent dielectric constant and dielectric loss at around 257 K, which was strongly suppressed by the application of 5 T magnetic field. The observation of magnetocapacitance effect confirms the magnetoelectric coupling, which originates from the magnetic and structural coupling.

为了打破氧化物钙钛矿中多铁性外壳电子结构的矛盾要求，选择了多铁性氟化物进行研究，其中铁电性和铁磁性可能都来自相同的磁性离子。通过固相反应制备纯相Ba ₅ Fe ₃ F _19-δ粉末。能量色散 X 射线光谱结果表明 Fe 缺乏。Fe ³⁺和Fe ²⁺的混合价态由X射线光电子能谱证实。通过压电响应力显微镜测量的振幅和相位滞后回线的观察表明 Ba ₅ Fe ₃ F 中的铁电性_19-δ。随温度变化的磁化曲线显示出随着温度的降低而持续增加，没有明显的相变。然而，温度相关的逆磁化率（χ）在 150 K 以上遵循居里 - 魏斯定律，居里 - 魏斯温度为 -55 K，表明 Fe 离子之间主要是反铁磁相互作用。该χT随着温度从 300 K 降低而降低，表明从高于 300 K 的温度开始弱反铁磁相互作用。对于低至 5 K 的磁相关磁化曲线没有观察到磁滞回线，表明缺乏长程排序。在 257 K 附近观察到随温度变化的介电常数和介电损耗的峰值，这被 5 T 磁场的应用强烈抑制。磁电容效应的观察证实了磁电耦合，它源于磁耦合和结构耦合。