On-line SPICE-SPIN+X Seminars
On-line Seminar: 17.12.2025 - 15:00 CEST
TBA
Bharat Jalan , University of Minnesota
TBA
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TBA
Please sign up here in order to get the Zoom link and regular announcements of the upcoming talks.
TBA
Please sign up here in order to get the Zoom link and regular announcements of the upcoming talks.
Please sign up here in order to get the Zoom link and regular announcements of the upcoming talks.
TBA
Please sign up here in order to get the Zoom link and regular announcements of the upcoming talks.
Please sign up here in order to get the Zoom link and regular announcements of the upcoming talks.
Please sign up here in order to get the Zoom link and regular announcements of the upcoming talks.
Please sign up here in order to get the Zoom link and regular announcements of the upcoming talks.
This talk will discuss two projects. The first concerns topological insulator/magnet samples made by mechanical stacking of exfoliated van der Waals flakes. The proximity interaction of the magnet with the topological surface state allows realization of the “parity anomaly” half-quantized Hall effect state at temperatures as high as 10 K -- the first materials system with a quantized anomalous Hall signal well above liquid-helium temperature. Direct capacitive measurements also indicate a large value of the exchange gap of approximately 10 meV. We speculate the reason for the higher temperature scale compared to previous topological insulator/magnet samples deposited by molecular beam epitaxy is that even a small amount of disorder due to interfacial mixing in deposited samples can push the topological surface state away from the interface and thereby weaken the exchange coupling to the magnet. The pristine interfaces formed by mechanical stacking of van der Waals layers eliminate this intermixing.
The second project concerns 3-terminal tunnel junctions (PtTe2/bilayer CrSBr/graphite) in which the A-type van der Waals antiferromagnet CrSBr acts as the tunnel barrier. Spin-filter tunneling through the CrSBr bilayer allows direct electrical measurements of antiferromagnetic resonance in the frequency domain. Furthermore, spin-orbit torque from the PtTe2 electrode provides electrically-tunable control over the magnetic damping and resonance linewidth. We find the interesting result that the spin-orbit torque is highly local, with the spin current from the PtTe2 electrode acting only on the individual spin sublattice layer adjacent to that electrode, with a negligible amount propagating to the next van der Waals layer.
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PDF file of the talk available here
Optical detection of magnetic resonance using quantum spin sensors (QSS) provides a spatially local and sensitive technique to probe spin dynamics in magnets. However, its utility as a probe of antiferromagnetic resonance (AFMR) remains an open question. We report the first experimental demonstration of optically detected AFMR in layered van der Waals antiferromagnets (AF) up to frequencies of 24 GHz. We leverage QSS spin relaxation due to low-frequency magnetic field fluctuations arising from collective dynamics of magnons excited by the uniform AFMR mode. First, through AFMR spectroscopy we characterize the intrinsic exchange fields and magnetic anisotropies of the AF. Second, using the localized sensitivity of the QSS we demonstrate magnon transport over tens of micrometers. Finally, we find that optical detection efficiency increases with increasing frequency. This showcases the dual capabilities of QSS as detectors of high frequency magnetization dynamics and magnon transport, paving the way for understanding and controlling the magnetism of antiferromagnets.
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