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arXiv · 2505.07957

Experimental Observation of Short-Range Magnetic Correlations in Amorphous Nb$_2$O$_5$ and Ta$_2$O$_5$ Thin Films

Y. V. Krasnikova·A. A. Murthy·D. Bafia·F. Crisa·A. Clairmont·Z. Sung·J. Lee·A. Cano·M. Shinde·D. M. T. van Zanten·M. Bal·A. Romanenko·A. Grassellino·R. Dhundhwal·D. Fuchs·T. Reisinger·I. M. Pop·A. Suter·T. Prokscha·Z. Salman
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Abstract

We use muon spin rotation/relaxation/resonance ($\mu$SR) to investigate the magnetic properties of niobium pentoxide (Nb$_2$O$_5$) and tantalum pentoxide (Ta$_2$O$_5$) thin films. In both oxides, we observe a magnetic response at the lowest available temperature of 2.8 K. This response appears to be structurally dependent: thermally oxidized Ta$_2$O$_5$ with low crystallinity demonstrates suppressed magnetism, while fully amorphous Ta$_2$O$_5$ demonstrates local static magnetism. In contrast, amorphous Nb$_2$O$_5$ is dominated by magnetic fluctuations and is strongly magnetically disordered compared to Ta$_2$O$_5$. Our results suggest that these fundamental differences in the magnetism of Ta and Nb oxides could explain the performance limitations in superconducting qubits and resonators.

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Y. V. Krasnikova, A. A. Murthy, D. Bafia, F. Crisa, A. Clairmont, Z. Sung, J. Lee, A. Cano, M. Shinde, D. M. T. van Zanten, M. Bal, A. Romanenko, A. Grassellino, R. Dhundhwal, D. Fuchs, T. Reisinger, I. M. Pop, A. Suter, T. Prokscha, Z. Salman. 2025-05-12. Experimental Observation of Short-Range Magnetic Correlations in Amorphous Nb$_2$O$_5$ and Ta$_2$O$_5$ Thin Films. https://doi.org/10.1103/b9yk-drfs

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