http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : Olivier Klein (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
-
-
Long-range Spin Transport using Magnon Phonon Coupling
Kyongmo An,Li Shi,Xiaoqin Li,Olivier Klein 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
In spintronics, this has revived interest for insulating materials and in particular garnets, which are the magnetic materials benefiting from the lowest magnetic damping. The sound wave attenuation coefficient in garnets is also exceptional, i.e. up to an order of magnitude lower than that in single crystalline quartz. In addition to the low damping of magnetic and sound waves, a strong coupling can be established between spin-waves (magnons) and lattice vibrations (phonons) through the magnetic anisotropy and strain dependence of the magneto crystalline energy in magnetic garnets. The magnetoelasticity leads to new hybrid quasiparticles (“magnon polarons”) when spin wave and acoustic wave dispersions cross [1]. This coupling has been exploited in the past to produce microwave acoustic transducers [2]. The adiabatic conversion between magnons and phonons in magnetic field gradients proves their strong coupling in yttrium iron garnet (YIG) [3]. I will first demonstrate that the spin waves can be strongly coupled to coherent transverse sound waves that have very long characteristic decay length and propagate ballistically over millimetric distances [4]. The experiment was performed at room temperature with a magnetic field applied perpendicular to the film. Our sample consists of two 200 nm thick YIG layers deposited on both sides of a 0.5 mm thick gadolinium gallium garnet (GGG) substrate. The circularly polarized standing sound waves couple to the magnetization oscillations in both layers. An interference pattern is observed and it is explained as the strong coupling of the magnetization dynamics of the two YIG layers either in phase or out of phase by the standing transverse sound waves. This long range coherent transport of spin by phononic angular momentum can add new functionalities to insulator spintronic circuits and devices. If time allows, I will also discuss my previous work on the nonequilibrium between magnons and phonons [5]. Here the local nonequilibrium is created optically within a focused laser spot and probed directly via micro-Brillouin light scattering. Through analyzing the deviation in the magnon number density from the local equilibrium value, we obtain the diffusion length of thermal magnons. By explicitly establishing and observing local nonequilibrium between magnons and phonons, this study represent an important step toward a quantitative understanding of various spin-heat coupling phenomena.
-
Coupling of Distant Magnets via Standing Acoustic Waves
Kyongmo An,Changsoo Kim,Chanyong Hwang,Olivier Klein 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2
We study the coupled dynamics of two magnets on both sides of a thick crystal spacer. The magnets communicate by acting as "speakers" as well as "microphones" for sound waves. The system can be tuned into tripartite hybridization by carefully tuning the two ferromagnetic resonance frequencies to a degenerate acoustic resonance of the crystal. Being in a regime where the interaction strength between the magnetic excitations is larger than their decay rate, the system is in the strong coupling regime in which the entire system of magnetization and lattice can only oscillate coherently. We show there that illumination of the bright and dark collective modes by a uniform microwave field depends on the parity of the phonon mode, which decides if the lattice displacement at the position of the two magnets is out-of-phase or in-phase. Depending on the parity of intermediate standing lattice waves, the interference is constructive or destructive, giving rise to the bright and dark collective modes. Our solid state realization consists of a half-millimeter thick slab of nonmagnetic gallium gadolinium garnet coated epitaxially on both sides by the ferrimagnet yttrium iron garnet. The magnetoelastic coupling in itself is not so strong so it is the exceedingly high crystal quality and long lifetimes of magnons and phonons in garnets that are key to unveil strong coupling. The frequency can be tuned by applied magnetic field strength and directions, while we measure the magnetization dynamics electrically by induced voltages in Pt contacts and microwave absorption. Besides the electrical detection, we demonstrate the detection of magnon-phonon coupling using the inelastic light scattering technique. By virtue of the local detection, we obtain the line width close to the intrinsic value of magnetic damping. A clear signature of magnon-phonon coupling will be shown as a dip in the magnetic resonance spectrum.
-
Hybrid fiber links for accurate optical frequency comparison
Lee, Won-Kyu,Stefani, Fabio,Bercy, Anthony,Lopez, Olivier,Amy-Klein, Anne,Pottie, Paul-Eric Springer-Verlag 2017 Applied physics. B, Lasers and optics Vol.123 No.4
<P>We present the experimental demonstration of a local two-way optical frequency comparison over a 43-km-long urban fiber network without any requirement for measurement synchronization. We combined the local two-way scheme with a regular active noise compensation scheme that was implemented on another parallel fiber leading to a highly reliable and robust frequency transfer. This hybrid scheme allowed us to investigate the major limiting factors of the local two-way comparison. We analyzed the contributions of the interferometers at both local and remote locations to the phase noise of the local two-way signal. Using the ability of this setup to be injected by either a single laser or two independent lasers, we measured the contributions of the demodulated laser instabilities to the long-term instability. We show that a fractional frequency instability level of 10(-20) at 10,000 s can be obtained using this simple setup after propagation over a distance of 43 km in an urban area.</P>
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
