30 октября 2018 г. в 17.00 Институт Физических Проблем им. П.Л. Капицы РАН приглашает всех желающих на семинар по магнетизму. Вход свободный
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30 октября 2018 года (ближайший вторник) в 17:00 в конференц-зале Институте Физических Проблем им. П.Л. Капицы РАН (Москва, ул. Косыгина, д. 2, второй этаж) состоится очередное заседание семинара по магнетизму. Как всегда, вход свободный, приглашаются все желающие.
Докладчик: Сергей Демокритов
Department of Physics, University of Muenster, 48149 Muenster, Germany
Термодинамика магнонного газа под воздействием спинового тока.
Thermodynamic characteristics of magnons driven by the spin-orbit torque
S. O. Demokritov
Department of Physics, University of Muenster, 48149 Muenster, Germany
Recent theoretical studies suggest that spin orbit-torque (SOT) can drive the magnon gas into a quasi-equilibrium state described by the Bose-Einstein statistics with non-zero chemical potential, suggesting the possibility of electrically-driven Bose-Einstein condensation (BEC) of magnons.
We have studied the effects of SOT on the magnon distribution in Permalloy (Py) over a broad spectral range, by utilizing the micro-focus Brillouin light scattering (BLS) spectroscopy. Pure spin current causing SOT was injected into Py due to the spin-Hall effect in the adjacent Pt layer. The BLS spectra, reflecting the current-dependent spectral density of magnons, allowed us to analyze the spectral magnon population function and determine the thermodynamic characteristics of the magnon gas. Our analysis clearly indicates that the magnon distribution can be described by the Bose-Einstein statistics expected for the quasi-equilibrium state. We determined the current-dependent chemical potential and effective temperature of the magnon gas, and showed that, for one polarization of the spin current, the effective temperature of the magnon gas becomes significantly reduced, while the chemical potential stays almost constant. In contrast, for the opposite polarization, the effective temperature remains nearly unaffected, while the chemical potential linearly increases with current, until it closely approaches the lowest-energy magnon state, indicating the possibility of spin current-driven Bose-Einstein condensation.