Abstract
Abstract The field of THz spintronics is a novel direction in the research field of nanomagnetism and spintronics that combines magnetism with optical physics and ultrafast photonics. The experimental scheme of the field involves the use of femtosecond laser pulses to trigger ultrafast spin and charge dynamics in thin films composed of ferromagnetic and nonmagnetic thin layers, where the nonmagnetic layer features a strong spin–orbit coupling. The technological and scientific key challenges of THz spintronic emitters are to increase their intensity and to shape the frequency bandwidth. To achieve the control of the source of the radiation, namely the transport of the ultrafast spin current is required. In this review, we address the generation, detection, efficiency and the future perspectives of THz emitters. We present the state-of-the-art of efficient emission in terms of materials, geometrical stack, interface quality and patterning. The impressive so far results hold the promise for new generation of THz physics based on spintronic emitters.
Highlights
Terahertz (THz) radiation covers a broad bandwidth of the electromagnetic spectrum from 100 GHz to 30 THz [1] lying between the microwave and the far infrared band.THz radiation is utilized by a number of scientific and research communities, ranging from chemistry and medicine to physics and material sciences
The field of THz spintronics is a novel direction in the research field of nanomagnetism and spintronics that combines magnetism with optical physics and ultrafast photonics
We review the recent developments in nanomagnetism and spintronics that allowed the first usage of ultrafast spin physics for THz emission
Summary
Terahertz (THz) radiation covers a broad bandwidth of the electromagnetic spectrum from 100 GHz to 30 THz [1] lying between the microwave and the far infrared band. Due to the inverse spin Hall effect (ISHE), the spin current is converted into a transient transverse charge current in the NM layer resulting in THz emission [4] This new source of THz radiation is an emerging topic subject to intensive research. For THz generation in spintronic THz emitters the physical mechanism is different and is based on the excitation of a spin current and the inverse spin Hall effect (ISHE), Figure 1. A femtosecond spin current pulse is launched in the ferromagnetic Co20Fe60B20 layer and drives terahertz transients at a Rashba interface between two nonmagnetic layers, Ag and Bi. In contrast to the THz emission in spintronic emitters via the inverse spin Hall effect, the inverse Rashba Edelstein effect transforms a nonzero spin density induced by the spin current injection into a charge current carried by interfacial states. The THz generation is suggested to be mainly caused by the nonthermal superdiffusive current near the two FM/dielectric interfaces
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