Collective spin excitations in bi-component magnonic crystals consisting of bi-layer Permalloy/Fe nanowires

Abstract

In the developing field of magnonics,it is very important to achieve tailoring of spin wave propagation by both a proper combination of materials with different magnetic properties and their nanostructuring on the submicrometric scale. We have exploited deep ultra-violet lithography, in combination with tilted shadow deposition technique, to fabricate arrays of closely spaced bi-layer nanowires (NWs), with separation d=100 nm and periodicity a=440 nm, having bottom and top layers made of Permalloy and Iron, respectively. The NWs have either rectangular cross section (bottom and upper layers of equal width) or L-shaped cross section (upper layer of half width). The frequency dispersion of collective spin wave excitations in the above bi-layered NWs arrays has been measured by the Brillouin light scattering technique while sweeping the wave vector perpendicularly to the wire length over three Brillouin zones of the reciprocal space. For the rectangular NWs, the lowest frequency fundamental mode, characterized by a quasi- uniform profile of the amplitude of the dynamic magnetization across the NW width, exhibits a sizeable and periodic frequency dispersion. A similar dispersive mode is also present in L-shaped NWs, but the mode amplitude is concentrated in the thin side of the NWs. The width and the center frequency of the magnonic band associated with the above fundamental modes has been analyzed, showing that both can be tuned by varying the external applied field. Moreover, for the L-shaped NWs it is shown that there is also a second dispersive mode,at higher frequency,characterized by an amplitude concentrated in the thick side of the NW. These experimental results have been quantitatively reproduced by an original numerical model that includes two-dimensional Green's function of the dipole field of the dynamic magnetization and interlayer exchange coupling between the layers.

arXiv comment17 pages, 5 figures

References in corpus (6)

• Brillouin light scattering studies of planar metallic magnonic crystals
• Strong asymmetry of microwave absorption by bi-layer conducting ferromagnetic films in the microstrip-line based broadband ferromagnetic resonance
• Spin waves in one-dimensional bi-component quasicrystals
• Thickness dependence of the degree of spin polarization of the electrical current in permalloy thin films
• Spin-wave dynamics in Permalloy/Cobalt magnonic crystals in the presence of a non-magnetic spacer
• Microwave magnetic dynamics in ferromagnetic metallic nanostructures lacking inversion symmetry

Cited by in corpus (9)

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• Reprogrammable magnonic band structure of layered Permalloy/Cu/Permalloy nanowires
• Ultrastrong magnon-magnon coupling and chiral spin-texture control in a dipolar 3D multilayered artificial spin-vortex ice
• Deterministic Field-free Switching of a Perpendicularly Magnetized Ferromagnetic Layer via the Joint Effects of Dzyaloshinskii-Moriya Interaction and Field-like Spin-orbit Torque: An Appraisal
• Applications of Nanomagnets as Dynamical Systems
• Collective spin waves in arrays of Permalloy nanowires with single-side periodically modulated width
• Coherent and dissipative coupling in a magneto-mechanical system
• Observation of band narrowing and mode conversion in two-dimensional binary magnonic crystal
• Observation of angle-dependent mode conversion and mode hopping in 2D annular antidot lattice