Centre Énergie, Matériaux et Télécommunications, INRS, 1650 boulevard Lionel-Boulet, Varennes, Québec, J3X 1S2, Canada.
Département de Génie Physique & Regroupement québécois sur les matériaux de pointe (RQMP), Polytechnique Montréal, Montréal (Québec), H3T 1J4, Canada.
Sci Rep. 2017 Jun 16;7(1):3712. doi: 10.1038/s41598-017-02742-9.
Epsilon ferrite (ε-FeO) is a metastable phase of iron(III) oxide, intermediate between maghemite and hematite. It has recently attracted interest because of its magnetocrystalline anisotropy, which distinguishes it from the other polymorphs, and results in a gigantic coercive field and a natural ferromagnetic resonance frequency in the THz range. Moreover, it possesses a polar crystal structure, making it a potential ferroelectric, hence a potential multiferroic. Due to the need of size confinement to stabilize the metastable phase, ε-FeO has been synthesized mainly as nanoparticles. However, to favor integration in devices, and take advantage of its unique functional properties, synthesis as epitaxial thin films is desirable. In this paper, we report the growth of ε-FeO as epitaxial thin films on (100)-oriented yttrium-stabilized zirconia substrates. Structural characterization outlined the formation of multiple in-plane twins, with two different epitaxial relations to the substrate. Transmission electron microscopy showed how such twins develop in a pillar-like structure from the interface to the surface. Magnetic characterization confirmed the high magnetocrystalline anisotropy of our film and revealed the presence of a secondary phase which was identified as the well-known magnetite. Finally, angular analysis of the magnetic properties revealed how the presence of twins impacts their azimuthal dependence.
ε 型铁酸亚铁（ε-FeO）是三氧化二铁的亚稳相，处于磁赤铁矿和赤铁矿之间。由于其磁晶各向异性，使其有别于其他多晶型体，从而产生巨大的矫顽力和太赫兹范围内的天然铁磁共振频率，它最近引起了人们的兴趣。此外，它具有极性晶体结构，使其成为潜在的铁电体，因此也是潜在的多铁体。由于需要尺寸限制来稳定亚稳相，ε-FeO 主要被合成作为纳米粒子。然而，为了有利于器件集成，并利用其独特的功能特性，希望将其合成作为外延薄膜。在本文中，我们报告了在（100）取向的钇稳定氧化锆衬底上外延生长ε-FeO 薄膜。结构特征描述了形成了多个面内孪晶，与衬底有两种不同的外延关系。透射电子显微镜显示了这种孪晶如何从界面以柱状结构发展到表面。磁性特征证实了我们的薄膜具有高的磁晶各向异性，并揭示了存在一种被称为众所周知的磁铁矿的次要相。最后，对磁性的角度分析揭示了孪晶的存在如何影响其方位依赖性。
