Spin-torque-driven mode hybridization and band engineering in nanopatterned magnonic crystals

Spin-wave propagation and its control at the nanoscale are central to developing reconfigurable magnonic and spintronic devices. Here, tunable mode coupling and band hybridization are demonstrated in a nanopatterned magnonic crystal through the effective use of inhomogeneous current-induced spin–orbit torque. The system consists of a Permalloy thin film interfaced with a heavy metal and patterned with a two-dimensional array of circular Co nanodots, forming a bicomponent magnonic crystal with spatially modulated magnetic and spin-torque parameters. Spin-wave band structures and modes are investigated using the plane-wave method. By solving the linearized Landau–Lifshitz equation, incorporating a field-like torque term, in the reciprocal lattice, a full magnonic bandgap is obtained. Current injection through the heavy-metal layer induces inhomogeneous spin–orbit coupling within the magnonic crystal, producing a periodic perturbation of the magnonic frequency and enabling dynamic control over spin-wave dispersion. A prominent avoided crossing between localized modes and propagating Damon–Eshbach-type modes is observed at a finite wave vector. The periodic effective spin-torque term drives band deformation, enhanced nanoscale mode mixing, and a tunable hybridization gap. Eigenmode analysis reveals the transition from confined standing modes to propagating modes, with spin-torque-controlled mode exchange and band repulsion governing the anticrossing position and magnitude in the spin-wave dispersion. These results demonstrate that spin–orbit torque effectively controls hybrid magnonic states, enabling tunable mode conversion and enhanced functional control over spin-wave behavior in magnonic crystals and spintronic devices.