A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature

Combining long-range magnetic order with polarity in the same structure is a prerequisite for the design of (magnetoelectric) multiferroic materials. There are now several demonstrated strategies to achieve this goal, but retaining magnetic order above room temperature remains a difficult target. Iron oxides in the +3 oxidation state have high magnetic ordering temperatures due to the size of the coupled moments. Here we prepare and characterize ScFeO3 (SFO), which under pressure and in strain-stabilized thin films adopts a polar variant of the corundum structure, one of the archetypal binary oxide structures. Polar corundum ScFeO3 has a weak ferromagnetic ground state below 356 Kthis is in contrast to the purely antiferromagnetic ground state adopted by the well-studied ferroelectric BiFeO3.

在同一晶体结构中同时实现长程磁有序与极性，是设计磁电多铁性材料 (magnetoelectric multiferroic materials) 的先决条件。目前已有多种经实验验证的策略可实现这一目标，但在室温以上维持磁有序仍是一项颇具挑战性的研究课题。处于+3氧化态的铁氧化物因耦合磁矩的尺度效应，具备较高的磁有序转变温度。本文中，我们制备并表征了钪铁氧体 (ScFeO3，SFO)：在压力条件与应变稳定的薄膜体系中，该材料会呈现刚玉结构 (corundum structure) 的极性变体——刚玉结构是典型的二元氧化物结构之一。极性刚玉型钪铁氧体在356 K以下呈现弱铁磁基态，这与研究较为深入的铁电材料铋铁氧体 (BiFeO3) 所采用的纯反铁磁基态截然不同。