Combinatorial Survey of Structural Phase Distribution and Magnetism in Fe‐Ge‐Te Composition‐Spread Thin Film Libraries

ABSTRACT

Magnetic 2‐dimensional (2D) van der Waals (vdW) materials have garnered tremendous attention. The vdW ferromagnet Fe ₅ Ge ₁ Te ₂ has a Curie temperature T _c of ≈ 270 K, which is tailorable by tuning the stoichiometry and the Fe deficiency to reach room temperature. To explore the expanded compositional space, we implemented combinatorial synthesis and high‐throughput characterization to investigate the structural phase distribution and ferromagnetism of a Fe‐Ge‐Te thin film library, which was prepared by magnetron co‐sputtering followed by annealing. Composition and structural property of the 177 pads in the library were characterized using wavelength dispersive spectroscopy (WDS) and X‐ray diffraction (XRD). We leverage unsupervised machine learning to cluster the XRD dataset into groups of compositions with similar structural phases, and further study the ferromagnetic properties via SQUID magnetometry and X‐ray magnetic circular dichroism (XMCD) across different clusters. The results are compared against magnetization and structural models calculated using DFT. We revealed that the hexagonal crystal structure is a critical prerequisite for ferromagnetism in this system, and that unexplored materials adopting this structure can be efficiently identified as possible ferromagnetic materials using our ML‐assisted framework. This workflow allows us to rapidly capture the composition‐structure‐property map across a broad compositional landscape of novel magnetic materials.