Magnon polarons, a type of hybridized excitations between magnons and phonons, were first reported in yttrium iron garnet as anomalies in the spin Seebeck effect responses. Here, we report an observation of antiferromagnetic (AFM) magnon polarons in a uniaxial AFM insulator Cr_{2}O_{3}. Despite the relatively higher energy of magnon than that of the acoustic phonons, near the spin-flop transition of ∼6 T, the left-handed magnon spectrum shifts downward to hybridize with the acoustic phonons to form AFM magnon polarons, which can also be probed by the spin Seebeck effect. The spin Seebeck signal is founded to be enhanced due to the magnon polarons at low temperatures.
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http://dx.doi.org/10.1103/PhysRevLett.125.217201 | DOI Listing |
Phys Rev Lett
February 2024
Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China.
We report a giant hysteretic spin Seebeck effect (SSE) anomaly with a sign reversal at magnetic fields much stronger than the coercive field in a (001)-oriented Tb_{3}Fe_{5}O_{12} film. The high-field SSE enhancement reaches 4200% at approximately 105 K over its weak-field value and presents a nonmonotonic dependence on temperature. The unexpected high-field hysteresis of SSE is found to be associated with a magnetic transition of double-umbrella spin texture in TbIG.
View Article and Find Full Text PDFPhotoacoustics
December 2023
Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany.
Phonons and magnons are prospective information carriers to substitute the transfer of charge in nanoscale communication devices. Our ability to manipulate them at the nanoscale and with ultimate speed is examined by ultrafast acoustics and femtosecond optomagnetism, which use ultrashort laser pulses for generation and detection of the corresponding coherent excitations. Ultrafast magnetoacoustics merges these research directions and focuses on the interaction of optically generated coherent phonons and magnons.
View Article and Find Full Text PDFNat Commun
September 2023
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, 210093, China.
Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, and are responsible for many exotic spintronic and magnonic phenomena. Despite long-term sustained experimental efforts in chasing for magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the direct observation of magnon polarons using neutron spectroscopy on a multiferroic FeMoO possessing strong magnon-phonon coupling.
View Article and Find Full Text PDFNat Commun
June 2023
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, 210093, Nanjing, China.
Two-dimensional (2D) magnetic systems possess versatile magnetic order and can host tunable magnons carrying spin angular momenta. Recent advances show angular momentum can also be carried by lattice vibrations in the form of chiral phonons. However, the interplay between magnons and chiral phonons as well as the details of chiral phonon formation in a magnetic system are yet to be explored.
View Article and Find Full Text PDFNat Commun
April 2023
FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED, Nijmegen, The Netherlands.
Magnetic materials play a vital role in energy-efficient data storage technologies, combining very fast switching with long-term retention of information. However, it has been shown that, at very short time scales, magnetisation dynamics become chaotic due to internal instabilities, resulting in incoherent spin-wave excitations that ultimately destroy magnetic ordering. Here, contrary to expectations, we show that such chaos gives rise to a periodic pattern of reversed magnetic domains, with a feature size far smaller than the spatial extent of the excitation.
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