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

doi:10.1103/b9yk-drfs

paper

Experimental Observation of Short-Range Magnetic Correlations in Amorphous Nb $_{2}$ O $_{5}$ and Ta $_{2}$ O $_{5}$ Thin Films

arXiv:2505.07957 · doi:10.1103/b9yk-drfs

Abstract

We use muon spin rotation/relaxation/resonance ( $I^¼$ 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.

15 pages, 15 figures

Experimental Observation of Short-Range Magnetic Correlations in Amorphous Nb2​O5​ and Ta2​O5​ Thin Films

Abstract

Experimental Observation of Short-Range Magnetic Correlations in Amorphous Nb $_{2}$ O $_{5}$ and Ta $_{2}$ O $_{5}$ Thin Films