The growing demand for strong permanent magnets such as neodymium magnets and the volatile prices of rare earth elements are stimulating the search for new hard magnetic materials that do not contain rare earth elements. At the same time, the increasing miniaturization of electronic circuits, evident in today's processors, is directing researchers' attention to structures on the order of nanometres in size, whose properties can differ significantly from those of bulk macroscopic materials. In this context, many systems are considered, such as Fe1-xCox alloys, iron-based L10 phases: FePt and FeNi, or L10 CoPt [1, 2].
Experimental and computational studies of ordered L10 FeNi thin films [3, 4] indicate that the L10 FeNi phase in the form of ultrathin films exhibits magnetic properties that allow potential applications. We decided to take another look at this material, and more specifically, the thin layers made of it with the surfaces (111), (010), and (001). For this purpose, we performed quantum calculations based on the full-potential local-orbital (FPLO) method using the density functional theory (DFT) implemented in the FPLO18 code [5].
Our research allowed us to determine the preferred direction of magnetization easy-axis in the considered systems. We also investigated changes in this direction as a function of film thickness. In the case of the systems with the surface (111), the deflection of the magnetization easy-axis from the [001] direction was observed, depending on the number of monolayers of the tested system. In addition, we determined changes in magnetic moments and energy differences of systems with magnetization consistent with particular crystallographic directions as a function of layer thickness.
The computational results obtained still require experimental confirmation. However, the predicted magnetization configurations, for example, in the direction oblique to the plane of the layer, may find applications in electronic devices.