Prieto Mauricio J, de Souza Caldas Lucas, Tănase Liviu C, Schmidt Thomas, Rodríguez de la Fuente Oscar
Department of Interface Science, Fritz-Haber-Institute of the Max-Planck-Society, Berlin, Germany.
Departamento de Física de Materiales, Universidad Complutense de Madrid, Madrid, Spain.
Ultramicroscopy. 2024 Jan;255:113855. doi: 10.1016/j.ultramic.2023.113855. Epub 2023 Sep 17.
The search of new properties in novel oxide heterostructures requires the exploration of new fabrication methods and the study, at the microscopic level, of the processes involved during the synthesis. We present a synchrotron-based spectromicroscopic investigation of a magnetite/hematite bilayer on Pt(111) grown in a two-step process by thermal evaporation and Low Energy Ion Bombardment (LEIB). The characterization includes the study of structural, electronic, chemical, and magnetic properties using X-ray Absorption Spectroscopy (XAS), Low Energy Electron Microscopy (LEEM), Photoemission Electron Microscopy (PEEM), or X-ray Magnetic Circular Dichroism (XMCD). The aim is to obtain microscopic information of the thin film before, during, and after the ion bombardment. Ion bombardment gradually transforms the topmost layers of the hematite thin film into a defective sub-oxide, where magnetite nuclei grow and coalesce with increasing ion doses. Two rotational domains of magnetite coexist, which are typically a few tens of nanometres large and do not grow significantly with temperature annealings. The incoherent growth of the magnetite nuclei favours the formation of stable twin boundaries (TBs) and antiphase boundaries (APBs). Dichroic spectra show the characteristics of the ferrimagnetic (FiM) order of magnetite, and the spatial distribution of magnetic domains shows no apparent correlation with the structural image, displaying smooth domains separated by diffuse frontiers. These findings illustrate the importance of a spectromicroscopic characterization of novel oxide heterostructures for potential future applications.
在新型氧化物异质结构中寻找新特性需要探索新的制备方法，并在微观层面研究合成过程中涉及的各种过程。我们展示了一项基于同步加速器的光谱显微镜研究，该研究针对通过热蒸发和低能离子轰击（LEIB）两步法在Pt(111)上生长的磁铁矿/赤铁矿双层结构。表征包括使用X射线吸收光谱（XAS）、低能电子显微镜（LEEM）、光发射电子显微镜（PEEM）或X射线磁圆二色性（XMCD）来研究结构、电子、化学和磁性特性。目的是获取离子轰击之前、期间和之后薄膜的微观信息。离子轰击逐渐将赤铁矿薄膜的最顶层转变为一种有缺陷的亚氧化物，随着离子剂量增加，磁铁矿核在其中生长并合并。磁铁矿的两个旋转畴共存，其典型尺寸为几十纳米，并且在温度退火时不会显著生长。磁铁矿核的非相干生长有利于形成稳定的孪晶界（TBs）和反相界（APBs）。二色性光谱显示出磁铁矿亚铁磁（FiM）序的特征，磁畴的空间分布与结构图像没有明显相关性，显示出由弥散边界分隔的平滑畴。这些发现说明了对新型氧化物异质结构进行光谱显微镜表征对于未来潜在应用的重要性。
