Abstract
The frequencies and linewidths of spin waves in one-dimensional (1D) and two-dimensional (2D) periodic superlattices of magnetic materials are found, using the Landau–Lifshitz–Gilbert equations. The form of the exchange field from a surface-torque-free boundary between magnetic materials is derived, and magnetic-material combinations are identified which produce gaps in the magnonic spectrum across the entire superlattice Brillouin zone for hexagonal and square-symmetry superlattices. The magnon gaps and spin-wave dispersion properties of a uniform magnetic material under the influence of a periodic electric field are presented. Such results suggest the utility of magnetic insulators for electric-field control of spin-wave propagation properties.
Highlights
Advancements in the control of spin-wave propagation and dynamics[1] have led to the demonstration of magnonic bose condensation[2] and coupling of electronic spin currents to spin waves in hybrid systems.[3]
For iron embedded in yttrium iron garnet (YIG), we demonstrate the existence of a gap throughout the superlattice Brillouin zone in the magnon spectrum for both square and hexagonal symmetry magnonic crystals
We consider a magnonic crystal composed of an array of innitely long cylinders of ferromagnetic material A embedded in a second ferromagnetic material B in a square or hexagonal lattice; the structures are shown in Fig. 1 and have lattice constant a and cylinder radius Rcyl
Summary
Advancements in the control of spin-wave propagation and dynamics[1] have led to the demonstration of magnonic bose condensation[2] and coupling of electronic spin currents to spin waves in hybrid systems.[3]. We consider a uniform magnetic material (YIG) under the in°uence of a periodic electriceld The presence of this periodic electriceld opens a substantial and tunable magnon gap within the dispersion and permits on/o® voltage-based control of spin-wave propagation. Two distinct forms for this exchangeeld in the presence of inhomogeneous material parameters (saturation magnetization and exchange constant) have been described in the literature,[14,29,30,31,32,33,34] to our knowledge it has not been pointed out that the di®erences in the solutions of the LLG equation obtained from the two e®ectiveelds produce large quantitiative di®erences in the spin-wave dispersion and lifewidths, nor has a derivation been presented of the correct form.
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