Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
MA: Fachverband Magnetismus
MA 9: Cooperative Phenomena: Spin Structures and Magnetic Phase Transitions
MA 9.6: Vortrag
Montag, 27. März 2023, 16:30–16:45, HSZ 401
Investigating the electronic charge and magnetic spin dynamics in the ferromagnetic semiconductor HgCr2Se4 using resistance fluctuation (noise) spectroscopy — •Charu Garg1, Zhilin Li2, Youguo Shi2, and Jens Müller1 — 1Institute of Physics, Goethe University, 60438 Frankfurt (M), Germany — 2Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190
The n-type HgCr2Se4 has been reported to exhibit a pronounced semiconductor-to-metal transition below and a CMR effect at the ferromagnetic transition at TC = 107 K. Our recent study of charge carrier dynamics [Phys. Rev B 105, 064404 (2022)] suggests isolated magnetic polarons forming at T > 2TC which coalesce at TC. In this talk, we discuss new results highlighting the strong correlation between the magnetic and electronic degrees of freedom that can lead to complex exchange pathways. Likely due to competing AF and FM interactions, we observe a distinctly slow decrease in resistance below the CMR transition. The striking dynamics of a distinct two-level fluctuations superimposed on 1/f-type noise corroborates a slowing down of charge carrier and/or magnetic dynamics. Further, below 20 K, a strong upturn in resistance and simultaneously in resistance noise down to 500 mK is observed and is speculated to be linked to the emergence of spiral type magnetic order. Our results demonstrate that the presence of pronounced electron-spin correlations plays a key role in the unconventional temperature dependence of resistance and CMR effect in this spinel.