Active manipulation of spin waves is essential for the development of magnon-based technologies. Here, we demonstrate programmable spin-wave filtering by resetting the spin structure of a pinned 90$^circ$ N{e}el domain wall in a continuous CoFeB film with abrupt rotations of uniaxial magnetic anisotropy. Using phase-resolved micro-focused Brillouin light scattering and micromagnetic simulations, we show that broad 90$^circ$ head-to-head or tail-to-tail magnetic domain walls are transparent to spin waves over a broad frequency range. In contrast, magnetic switching to a 90$^circ$ head-to-tail configuration produces much narrower domain walls at the same pinning locations. Spin waves are strongly reflected by a resonance mode in these magnetic domain walls. Based on these results, we propose a magnetic spin-wave valve with two parallel domain walls. Switching the spin-wave valve from an open to a close state changes the transmission of spin waves from nearly 100% to 0% at the resonance frequency. This active control over spin-wave transport could be utilized in magnonic logic devices or non-volatile memory elements.
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