Layer Ordering Effects on Spintronic THz Emission Probed by PNR (LOR-THz)

Magnetic multilayers are being explored as possible THz emitters (microwave to infrared range) due to their relative simplicity to prepare and integration with existing spintronics technology. In such multilayers, electromagnetic terahertz (THz) waves can be generated by femtosecond-laser excitation of spintronic stacks via the conversion of transient, optically excited spin states into ultrafast charge currents. The development of THz emitters and sensors holds immense potential for next-generation telecommunications, imaging, and sensing. In spintronic based emitters, the strength of the THz output is governed by the efficiency of spin current generation, transmission, and spin-to-charge conversion. This can be highly sensitive to the magnetic and structural properties at buried ferromagnet/non-magnetic metal interfaces, which are inaccessible using conventional X-ray reflectivity or bulk magnetometry techniques. Indeed, our preliminary results show that the sequence of layers in the stack significantly impacts THz emission, with certain W- and Fe-based configurations yielding much higher output compared to inverted structures.

This proposal seeks beamtime on POLREF instrument that will resolve depth-dependent magnetisation in spintronic trilayers on glass substrates. The central focus is to understand how layer ordering—specifically W/Py/Pt vs. Pt/Py/W—affects magnetisation profiles, roughness, and ultimately the THz emission performance.