Dynamic terahertz wave propagation through Al/Ni based multilayer spin valve structures

Metal-based magnetic multilayers are primarily responsible for giant-magnetoresistance (GMR) that play a pivotal role in magnetic memory devices besides other spintronic applications. Spin-dependent conduction of electrons steered by spin-dependent scattering across interfaces of the ferromagnetic (FM)/nonmagnetic multilayers lies at the core of GMR phenomena. In this context, the thickness dependent magnetoresistive effect in five-layer Al/Ni/Al/Ni/Al spin valve structures is explored through contactless terahertz (THz) spectroscopy. Our experiments reveal magnetic field dependent conductivity enhancement in the multilayer configuration of a FM (nickel, Ni) layer and a nonmagnetic (aluminum, Al) spacer layer under the application of relatively low intensity magnetic fields (0–30 mT) manifesting a substantial ground for low power THz magnetism. In addition, influence of similar magnetic fields is probed for relatively thicker spacers (10 nm ≤ x ≤ 20 nm) that can form a platform for dynamically controllable THz devices. Our studies demonstrate a maximum THz peak amplitude modulation of around 48% for a 10 nm thick nonmagnetic spacer layer (Al layer) along with a significant relative modulation (∼97%) in THz conductivities. Such tuning of THz characteristics bears great potential in realizing dynamically reconfigurable THz and magnetoresistive devices by suitably exploiting multilayer spin valve configuration.