Dresden 2026 – scientific programme
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MA: Fachverband Magnetismus
MA 57: Thin Films: Magnetic Coupling Phenomena / Exchange Bias and Magnetic Anisotropy
MA 57.5: Talk
Friday, March 13, 2026, 10:30–10:45, POT/0112
Two-component anomalous Hall and Nernst effects in anisotropic Fe4−xGexN thin films — •Jakub Vít1, Petr Levinský1, Robin K. Paul2, Imants Dirba2, and Karel Knížek1 — 1Institute of Physics, Prague, Czechia — 2TU Darmstadt
50-500 nm thin films of Fe4−xGexN (x=0–1) were fabricated onto MgO substrates by magnetron sputtering. The Hall and Nernst effects were measured, complemented with structural and magnetic characterizations, electron microscopy and DFT calculations. Fe4N is cubic, whereas a small tetragonal distortion is found in Fe4−xGexN films for x>0.35. The tetragonal samples with x=0.8 and 1 show two-component behavior in the Hall and Nernst effect hysteresis loops, which can be analyzed as a sum of positive and negative loops with different saturation fields. This unusual behavior is due to a combination of several factors: (1) Co-existence of two different crystallographic orientations in the tetragonal thin films. (2) Opposite sign of the anomalous Hall&Nernst effects (AHE&ANE) for the direction of magnetization along the a and c-axis. (3) Strong easy-plane magnetic anisotropy, responsible for different saturation fields for a and c-axis.
The maximum ANE was determined to be 0.9 V/K for x=0 at room temperature, and -0.85 V/K for x=1 at T=50 K. The rapid increase of ANE for Fe3GeN from low temperatures indicates that, were it not for its low TC (≈100 K), it could surpass ANE of Fe4N. This observation is consistent with our theoretical assumptions and motivates further research of doped Fe4N for which ANE enhancement is predicted by DFT calculations. (Preprint of this research: [arXiv 2511.14305])
Keywords: anomalous Hall effect; anomalous Nernst effect; iron nitrides; thin films; magnetic anisotropy