Spin Pumping in Electrodynamically Coupled Magnon-Photon Systems

Abstract

We use electrical detection, in combination with microwave transmission, to investigate both resonant and non-resonant magnon-photon coupling at room temperature. Spin pumping in a dynamically coupled magnon-photon system is found to be distinctly different from previous experiments. Characteristic coupling features such as modes anti-crossing, line width evolution, peculiar line shape, and resonance broadening are systematically measured and consistently analyzed by a theoretical model set on the foundation of classical electrodynamic coupling. Our experimental and theoretical approach pave the way for pursuing microwave coherent manipulation of pure spin current via the combination of spin pumping and magnon-photon coupling. PACS numbers:Coupling between electrodynamics and magnetization dynamics is a subject of cross-disciplinary and longstanding interest.The nuclear magnetic resonance (NMR) community has studied this effect for decades by measuring the radiation damping of NMR [1]. Engineers have routinely utilized this effect for designing microwave [2] and THz devices [3]. In condensed matter physics, such a coupling leads to the magnon polariton [4], which is an elementary excitation characterized by an intrinsic excitation gap between ferromagnetic resonance (FMR) and ferromagnetic antiresonance [5]. Extrinsically, classical coupling of magnetization dynamics with its electrodynamic surrounding causes Faraday induction of both NMR [6] and FMR [7]. From the perspective of quantum physics, resonant spin-photon coupling plays a central role in utilizing quantum information [8].In 2010, a theoretical work of Soykal and Flatté [9] sparked excitement in the community of spintronics for studying the strong field interaction of magnons and microwave photons. Pioneering experiments have been performed at cryogenic temperatures by Huebl et al. [10] and Tabuchi et al. [11] on the ferromagnetic insulator Yttrium iron garnet (YIG) placed on/in a microwave cavity, in which a large normal mode splitting was found in the transmission measurements, indicating large quantumcoherent magnon-photon coupling. In October 2014, an experimental breakthrough was made by Zhang et al.[12], who demonstrated Rabi-oscillations of the coupled magnon-photon system at room temperature. In the same month, an ultrahigh cooperativity of 10 5 between magnon and photon modes was reported [13]. These exciting works reveal just the tip of the iceberg of the new field of cavity spintronics. * Current affiliation: Department of Physics and Astronomy, University of Denver, Colorado, 80208, USA † Electronic address: hu@physics.umanitoba.ca; URL: http://www.physics.umanitoba.ca/∼hu So far, experiments in this emerging field were performed by measuring either the transmission (S 21 ) or reflection coefficient (S 11 ) of the microwave cavity loaded with a YIG sample. The coupling strength was obtained by fitting these S parameters to the microwave input-output formalism with an added self-energy term attributed to the magnon-photon coupling. This sta...

On-chip artificial magnon-polariton device for voltage control of electromagnetically induced transparency

“…In light of this principle, a cavity magnon polariton (CMP) has been recently studied in a coupled magnon-cavity photon system 2 , where the general feature of the CMP is described in a concise classical model 2 which accurately highlights the key physics of phase correlation between the cavity and magetization resonances. This general CMP model can be used to quantitatively analyze the characteristic features of magnon-photon coupling experiments recently performed by many different groups [2][3][4][5][6][7][8][9][10] , in which a low damping bulk ferromagnetic insulator is set either on-top of a superconducting co-plannar waveguide or inside a high quality 3D microwave cavity.…”

Indirect coupling between two cavity modes via ferromagnetic resonance

“…Recently, strong coupling between a microwave cavity mode and ferromagnetic resonance (FMR) has been realized at room temperature [6][7][8][9][10][11][12][13][14][15][16][17] . Exchange interactions lock the high density of spins in YIG into a macro-spin state, leading to strong coupling with a cavity mode which can be adjusted using an external magnetic field.…”

Thermal control of the magnon-photon coupling in a notch filter coupled to a yttrium iron garnet/platinum system

“…The sign reversal of V shows that the measured signal is not produced by a possible thermoelectric effect, induced by the microwave absorption. The strong coupling in the spin pumping signal (predicted by Cao et al 14 ) has been experimentally observed in a YIG(2.6-2.8µm)/Pt system for which the spin sink layer presents a thickness of 5 7 and 10 nm 6,8 . Even though the S21 parameter illustrates in Fig.…”

“…Magnon-photon coupling has been investigated in microwave resonators (three-dimensional cavity [1][2][3][4][5][6][7][8][9][10] and planar configuration [11][12][13] ) loaded with a ferrimagnetic insulator such as Yttrium Iron Garnet (YIG, thin film and bulk). More recently, research groups 6-8 have developed an electrical method to detect magnons coupled with photons.…”