Work

Elaboration of the magnetically frustrated GeFe2O4 spinel thin films by pulsed laser deposition

Year: 2025

Type: article

Abstract: Magnetic frustration is a significant focus of research in condensed matter physics, where competing spin-spin interactions give rise to emergent phenomena that challenge conventional understanding and topological effects with potential applications in quantum technologies. The direct spinel GeFe₂O₄ has recently garnered renewed interest for the plethora of magnetic behaviours it is able to demonstrate. Here, we report about the pioneering stabilization of GeFe2O4 in the form of thin films by pulsed laser deposition on MgO (001) substrates. The ablation procedure has been optimized to counterbalance the large volatility of the Ge species compared to the Fe ones, granting a fine control over the compositional homogeneity and stoichiometry of the films. Atomic force microscopy measurements rendered thin film surfaces with very low roughness values in the range of 0.2 nm, and X-ray diffraction data confirmed the epitaxial growth of the films and their high crystallinity with no detectable presence of spurious phases. SQUID magnetometry measurements revealed the expected antiferromagnetic behaviour, though with ordering temperatures larger than the expected bulk value. This discrepancy could be explained accounting for a small deviation from the direct spinel structure, as unveiled by resonant elastic X-ray scattering measurements, and from the resulting partial occupation of the tetrahedral sites by Fe atoms. Finally, varying the laser fluence we could tune the Fe/Ge ratio and provide a control over the ordering temperature from a modification of the spin-spin super-exchange network paths. Our results pave the way to further studies to explore emergent magnetic properties in GeFe₂O₄-based heterostructures.

Source: Materials Chemistry and Physics

DOI: 10.1016/j.matchemphys.2025.130831