New theory proposed for optimizing material choice in terahertz spintronics devices

While most parts of the electromagnetic spectrum have been adopted in many of today’s technology, the frequency band lying between microwaves and visible light, known as terahertz radiation, have seen relatively little use. Scientists look to make use of this so-called THz gap with antiferromagnets spintronics, which utilize materials that can tap into these little-used frequencies, and unlike ferromagnets, can operate without an external magnetic field.

Stremoukhov et al. propose an approximate nonlinear theory for a canted antiferromagnet-platinum bilayer spintronic terahertz-frequency emitter. The theory can be used to optimize decisions for choosing antiferromagnetic and heavy metal materials for desired THz generation and detection.

The authors demonstrated in theory that a bilayered antiferromagnet-based heterostructure can be used as a nonlinear terahertz-frequency emitter, where the amplitude of the output excitation on the fundamental frequency varies nonlinearly with the amplitude of the electromagnetic pump pulse.

The model accounts for the excitation of nonlinear oscillations of the Néel vector, which describes the macroscopic magnetic dynamic in the antiferromagnets. Fourier spectra were used to determine the bands of nonlinear excitation. An averaging method then provides the resulting envelope function of an oscillating output electromagnetic field.

“At this point, it’s essential to go deeper and estimate possible operating characteristics of AFM/HM-based detectors from the engineering point of view,” said Pavel Stremoukhov, an author on the paper. “This will give a better understanding of the ability to applying it in industry.”

The group hopes it will help experimentalists explore potential materials more efficiently. Stremoukhov said they look to continue work in antiferromagnetic spintronics, including exploring electrical control of THz frequency generated in such structures.

Source: “Spintronic terahertz-frequency nonlinear emitter based on the canted antiferromagnet-platinum bilayers,” by P. Stremoukhov, A. Safin, M. Logunov, S. Nikitov, and A. Kirilyuk, Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5090455 .