Separation of emission mechanisms in spintronic terahertz emitters

Liu, Yongshan; Cheng, Houyi; Xu, Yong; Vallobra, Pierre; Eimer, Sylvain; Zhang, Xiaoqiang; Wu, Xiaojun; Nie, Tianxiao; Zhao, Weisheng

doi:10.1103/physrevb.104.064419

Cited by 31 publications

(28 citation statements)

References 35 publications

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“…Figure 3 a,b plots the

(red) and

(blue) in the Pt/CoFeB/Ta and Ta/CoFeB/Pt samples. The THz peak amplitude by

reaches around 37% in magnitude compared with

, which is consistent with the result reported by Liu et al [ 51 ]. The most remarkable finding is that THz emission efficiency of a trilayer stack can be improved by optimizing the order of the Pt and Ta layers.…”

Section: Resultssupporting

confidence: 91%

Terahertz Emission Spectroscopy of Ultrafast Coupled Spin and Charge Dynamics in Nanometer Ferromagnetic Heterostructures

Jiang

Jin

et al. 2022

Nanomaterials

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Due to its high sensitivity and because it does not rely on the magneto-optical response, terahertz (THz) emission spectroscopy has been used as a powerful time-resolved tool for investigating ultrafast demagnetization and spin current dynamics in nanometer-thick ferromagnetic (FM)/heavy metal (HM) heterostructures. Here, by changing the order of the conductive HM coating on the FM nanometer film, the dominant electric dipole contribution to the laser-induced THz radiation can be unraveled from the ultrafast magnetic dipole. Furthermore, to take charge equilibration into account, we separate the femtosecond laser-induced spin-to-charge converted current and the instantaneous discharging current within the illuminated area. The THz emission spectroscopy gives us direct information into the coupled spin and charge dynamics during the first moments of the light–matter interaction. Our results also open up new perspectives to manipulate and optimize the ultrafast charge current for promising high-performance and broadband THz radiation.

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“…Figure 3 a,b plots the

(red) and

(blue) in the Pt/CoFeB/Ta and Ta/CoFeB/Pt samples. The THz peak amplitude by

reaches around 37% in magnitude compared with

Section: Resultssupporting

confidence: 91%

Terahertz Emission Spectroscopy of Ultrafast Coupled Spin and Charge Dynamics in Nanometer Ferromagnetic Heterostructures

Jiang

Jin

et al. 2022

Nanomaterials

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“…Ultrashort laser pulse has the capacity to control magnetization at subpicosecond timescale [1,2]. It is two to three orders of magnitude faster compared to the conventional methods for manipulating spins, including magnetic [3] or electric fields [4], heat [5], strains [6], spin-transfer torque [7], as well as spin-orbit torque [8].…”

Section: Introductionmentioning

confidence: 99%

Role of spin-lattice coupling in ultrafast demagnetization and all optical helicity-independent single-shot switching in Gd1−x−yTbyCox alloys

et al. 2022

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All optical switching (AOS) of magnetization exhibits a high potential for ultrafast and energy-efficient memory applications. Many works have been carried out in the area of AOS, including its observation in a wide variety of ferromagnetic or ferrimagnetic materials, and the exploration of the parameters for the achievements of AOS such as the laser fluence and helicity, and duration of laser pulses. A large majority of all optical helicity-independent single-shot switching (AO-HIS) has been observed in Gd-based rare-earth transition-metal ferrimagnets. It is then necessary to explore the unique role of Gd in AO-HIS mechanism, compared with other rare-earth elements. Here, we engineered Gd 1−x−y Tb y Co x alloys and investigated the influence of the Tb concentration on the magnetization dynamics via static Kerr microscope and time-resolved magneto-optical Kerr effect (TR-MOKE) measurements. The ultrafast demagnetization time at low fluence is found to be independent of Tb concentration, while both the range of laser fluence and pulse duration allowing for AO-HIS becomes narrower with increasing the Tb concentration. The TR-MOKE signal K / K_sat ∼ 10 ps after the laser pulse excitation decreases with increasing either the Tb concentration or the pulse duration. The fact that AO-HIS is prohibited by increasing the Tb content is explained by considering a larger damping for Tb than Gd in atomistic simulations. Our results are well explained by the fact that angular momentum can be transferred from Gd to Co resulting in the magnetization switching, whereas for Tb it is dissipated through the lattice due to the large spin-orbit coupling, instead of being transferred between Tb and Co.

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“…We then use a terahertz time-domain spectroscopy (THz-TDS) system (Figure S1a) to characterize the transmission properties of our fabricated metasurface array with different eigen polarizations. The study of the terahertz emission and modulation of the device were carried out with a home-built THz time-domain spectrometer . The femtosecond laser pulse used in the experiment is generated by an amplified Ti:sapphire laser source with 800 nm central wavelength, a 35 fs pulse duration, and an 1 kHz repetition rate.…”

Section: Resultsmentioning

confidence: 99%

“…The study of the terahertz emission and modulation of the device were carried out with a home-built THz time-domain spectrometer. 62 The femtosecond laser pulse used in the experiment is generated by an amplified Ti:sapphire laser source with 800 nm central wavelength, a 35 fs pulse duration, and an 1 kHz repetition rate. We pumped the W (2 nm)/CoFeB (2 nm)/Pt (2 nm) STE with a 170 mW, 8 mm diameter laser and a static in-plane field of 100 mT magnetization (NdFeB magnet).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Flexible Control of Broadband Polarization in a Spintronic Terahertz Emitter Integrated with Liquid Crystal and Metasurface

Sun

et al. 2022

ACS Appl. Mater. Interfaces

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Flexible polarization control of the terahertz wave in the wide bandwidth is crucial for numerous applications, such as terahertz communication, material characterization, imaging, and biosensing diagnosis. However, this promise is impeded by the operating bandwidth of circular polarization states, control modes, and the efficiency of the regulation. Here, we report a spintronic terahertz emitter integrated with phase complementary elements, consisting of a liquid crystal and metasurface, to achieve broadband polarization control with high flexibility. This strategy allows the broadband conversion between linear, elliptical, and circular polarization by changing the rotation angle to modulate the space-variant Pancharatnam–Berry phase. The device is characterized with a terahertz time-domain spectroscopy system, demonstrating that the ellipticity of the circular polarization state could keep greater than 0.9 in 0.60–0.99 THz. In the case of an external electro-magnetic field, further polarization modulation experiments are carried out to provide multiple conversion approaches for multi-azimuth. We first propose a method of full broadband polarization state control of the terahertz emitter based on Pancharatnam–Berry phase modulation and an external electro-magnetic field. We believe that such integrated devices with broadband working bandwidth and multiple control modes will make valuable contributions to the development and multi-scene applications of ultrafast terahertz technologies.

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Separation of emission mechanisms in spintronic terahertz emitters

Cited by 31 publications

References 35 publications

Terahertz Emission Spectroscopy of Ultrafast Coupled Spin and Charge Dynamics in Nanometer Ferromagnetic Heterostructures

Terahertz Emission Spectroscopy of Ultrafast Coupled Spin and Charge Dynamics in Nanometer Ferromagnetic Heterostructures

Role of spin-lattice coupling in ultrafast demagnetization and all optical helicity-independent single-shot switching in Gd1−x−yTbyCox alloys

Flexible Control of Broadband Polarization in a Spintronic Terahertz Emitter Integrated with Liquid Crystal and Metasurface

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