THz generation by exchange-coupled spintronic emitters

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Abstract
The mechanism of THz generation in ferromagnet/metal (F/M) bilayers has been typically ascribed to the inverse spin Hall effect (ISHE). Here, we fabricated Pt/Fe/Cr/Fe/Pt multilayers containing two back-to-back spintronic THz emitters separated by a thin (tCr≤ 3nm) wedge-shaped Cr spacer. In such an arrangement, magnetization alignment of the two Fe films can be controlled by the interplay between Cr-mediated interlayer exchange coupling (IEC) and an external magnetic field. This in turn results in a strong variation of the THz amplitude A, with A↑↓ reaching up to 14 times A↑↑ (arrows indicate the relative alignment of the magnetization of the two magnetic layers). This observed functionality is ascribed to the interference of THz transients generated by two closely spaced THz emitters. Moreover, the magnetic field dependence A(H) shows a strong asymmetry that points to an additional performance modulation of the THz emitter via IEC and multilayer design.
Funding Information
  • U.S. Department of Energy (DE-SC0022473, DE-SC0022473, DE-SC0022473, DE-SC0022473)

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