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Probing the magnetic polaron state in the ferromagnetic semiconductor HgCr2Se4 with muon-spin spectroscopy and resistance-fluctuation measurements

Mitschek, Merlin; Hicken, Thomas J.; Yang, Shuai; Wilson, Murray N.; Pratt, Francis L.; Wang, Chennan; Blundell, Stephen J.; Li, Zhilin; Li, Yongqing; Lancaster, Tom; Müller, Jens

Probing the magnetic polaron state in the ferromagnetic semiconductor HgCr2Se4 with muon-spin spectroscopy and resistance-fluctuation measurements Thumbnail


Authors

Merlin Mitschek

Shuai Yang

Murray N. Wilson

Francis L. Pratt

Chennan Wang

Stephen J. Blundell

Zhilin Li

Yongqing Li

Jens Müller



Abstract

Combined resistance noise and muon-spin relaxation (μSR) measurements of the ferromagnetic semiconductor HgCr2Se4 suggest a degree of magnetoelectric coupling and provide evidence for the existence of isolated magnetic polarons. These form at elevated temperatures and undergo a percolation transition with a drastic enhancement of the low-frequency 1/ f -type charge fluctuations at the insulator-to-metal transition at ∼95–98 K in the vicinity of the magnetic ordering temperature TC ∼ 105–107 K. Upon approaching the percolation threshold from above, the strikingly unusual dynamics of a distinct two-level fluctuator superimposed on the 1/ f noise can be described by a slowing down of the dynamics of a nanoscale magnetic cluster, a magnetic polaron, when taking into account an effective radius of the polaron depending on the spin correlation length. Coinciding temperature scales found in μSR and noise measurements suggest changes in the magnetic dynamics over a wide range of frequencies and are consistent with the existence of large polarized and domain-wall-like regions at low temperatures, that result from the freezing of spin dynamics at the magnetic polaron percolation transition.

Citation

Mitschek, M., Hicken, T. J., Yang, S., Wilson, M. N., Pratt, F. L., Wang, C., …Müller, J. (2022). Probing the magnetic polaron state in the ferromagnetic semiconductor HgCr2Se4 with muon-spin spectroscopy and resistance-fluctuation measurements. Physical Review B, 105(6), Article 064404. https://doi.org/10.1103/physrevb.105.064404

Journal Article Type Article
Acceptance Date Jan 13, 2022
Online Publication Date Feb 3, 2022
Publication Date Feb 1, 2022
Deposit Date Feb 7, 2022
Publicly Available Date Jun 14, 2022
Journal Physical Review B
Print ISSN 2469-9950
Electronic ISSN 2469-9969
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 105
Issue 6
Article Number 064404
DOI https://doi.org/10.1103/physrevb.105.064404
Related Public URLs https://arxiv.org/abs/2111.08990

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Copyright Statement
Reprinted with permission from the American Physical Society: Mitschek, Merlin, Hicken, Thomas J., Yang, Shuai, Wilson, Murray N., Pratt, Francis L., Wang, Chennan, Blundell, Stephen J., Li, Zhilin, Li, Yongqing, Lancaster, Tom & Müller, Jens (2022). Probing the magnetic polaron state in the ferromagnetic semiconductor HgCr2Se4 with muon-spin spectroscopy and resistance-fluctuation measurements. Physical Review B 105(6): 064404. © (2022) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.





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