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arXiv · 2610.29635

Confirmation of complex non-collinear Fe(II) spin ordering in the iron oxychalcogenide La$_2$O$_2$Fe$_2$OSe$_2$ by broad range $^{139}$La-NQR

Tillmann Weinhold·Jerin Abraham George·Cornelius Herrmann·Domenic Nowak·Rajib Sarkar·Felix Seewald·Rowena Wachtel·Sabine Wurmehl·Bernd Büchner·Hans-Henning Klauss
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Abstract

The transition metal oxychalcogenide La$_2$O$_2$Fe$_2$OSe$_2$ exhibits a non-collinear spin-ice like antiferromagnetic ordering below $T_N \approx $ 90 K due to complex magnetic exchange interactions and axial single-ion anisotropy of Fe$^{2+}$ spins. The magnetic structure was deduced/determined from combined $^{57}$Fe Mössbauer spectroscopy and $^{139}$La-NMR on polycrystalline specimen. In this work, we present zero-field $^{139}$La-NQR investigations on polycrystalline La$_2$O$_2$Fe$_2$OSe$_2$ in a broad frequency and temperature range between 2.8 - 20 MHz and 4.2 - 100 K. The measured resonances at $ν_Q$, $2 \, ν_Q$, and $3 \, ν_Q$ are fully consistent with the previous NMR studies and also with the magnetic structure. A substantial modification of the electric field gradient at the La-position below $T_N$ is inconsistent with the current investigations.

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Tillmann Weinhold, Jerin Abraham George, Cornelius Herrmann, Domenic Nowak, Rajib Sarkar, Felix Seewald, Rowena Wachtel, Sabine Wurmehl, Bernd Büchner, Hans-Henning Klauss. 2026-10-21. Confirmation of complex non-collinear Fe(II) spin ordering in the iron oxychalcogenide La$_2$O$_2$Fe$_2$OSe$_2$ by broad range $^{139}$La-NQR. https://arxiv.org/abs/2610.29635

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