Abstract
Magnetoelectric multiferroics such as rare earth manganites host nonreciprocal behavior driven by low symmetry, spin-orbit coupling, and toroidal moments, although less has been done to explore whether lanthanides like Er3+ might extend functionality into the hard infrared for optical communications purposes. In this work, we reveal nonreciprocity in the f-manifold crystal field excitations of h-Lu0.9Er0.1MnO3. In addition to contrast in the highest fields, we demonstrate nonreciprocity at technologically-relevant energy scales--specifically in the E-, S-, and C-bands of the telecom wavelength range--and at low magnetic fields and room temperature. In fact, the low field behavior is consistent with possible altermagnetism. These findings advance the overall understanding of localized excitations in rare earth-containing systems and pave the way for entirely new types of telecom applications.
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The datasets generated and/or analyzed during the current study are not publicly available due to active intellectual property considerations, but are available from the corresponding authors upon reasonable request.
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Acknowledgements
Research at the University of Tennessee is supported by Condensed Matter Physics, Division of Materials Research, U. S. National Science Foundation (DMR-2226109). Work at Rutgers is funded by the W. M. Keck Foundation grant to the Keck Center for Quantum Magnetism at Rutgers University. The National High Magnetic Field Laboratory is supported by the National Science Foundation Cooperative Agreement DMR-2128556, the State of Florida, and the U.S. Department of Energy. H.S.K. was supported by the Basic Science Research Program through the National Research Foundation of Korea, funded by the Ministry of Science and ICT [Grant No. NRF-2020R1C1C1005900, RS-2023-00220471].
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J.L.M. and S.W.C. designed the study. X.X. grew the crystals under the supervision of S.W.C. K.A.S., S.A.C., and J.L.M. performed the pulsed field magneto-optical spectroscopies. K.A.S. and Y.G. analyzed the data with guidance from J.L.M. K.A.S. and J.L.M. developed the figures and wrote the manuscript. K.A.S., Y.G., X.X., H.S.K., S.W.C., S.A.C., and J.L.M. commented on the text.
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Authors K.A.S., Y.G., X.X., H.S.K., S.A.C., and J.L.M. declare no competing interests. Author S.W.C. serves as an editor of this journal and had no role in the peer-review or decision to publish this paper. Author S.W.C. declares no competing interests.
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Smith, K.A., Gu, Y., Xu, X. et al. Optical diode effect at telecom wavelengths in a polar magnet. npj Quantum Mater. (2026). https://doi.org/10.1038/s41535-026-00848-w
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DOI: https://doi.org/10.1038/s41535-026-00848-w
