Competing anisotropies in exchange-biased nanostructured thin films

Abstract

The magnetic anisotropies of a patterned, exchange biased Fe 50 Mn 50 /Ni 80 Fe 20 system are studied using ferromagnetic resonance, supplemented by Brillouin light scattering experiments and Kerr magnetometry. The exchange biased bilayer is partially etched into an antidot geometry so that the system approximates a Ni 80 Fe 20 layer in contact with antidot structured Fe 50 Mn 50 . Brillouin light scattering measurements of the spin wave frequency dependence on the wave vector reveal a magnonic band gap as expected for a periodic modulation of the magnetic properties. Analysis of the ferromagnetic resonance spectra reveals eightfold and fourfold contributions to the magnetic anisotropy. Additionally, the antidot patterning decreases the magnitude of the exchange bias and modifies strongly its angular dependence. Softening of all resonance modes is most pronounced for the applied magnetic field aligned within 10• of the antidot axis, in the direction of the bias. Given the degree to which one can tailor the ground state, the resulting asymmetry at low frequencies could make this an interesting candidate for applications such as selective/directional microwave filtering and multistate magnetic logic.

Brillouin light scattering studies of 2D magnonic crystals

“…As anticipated in the introduction (section 1), a complementary approach to realizing a 2D MC is to drill a regular array of holes in a continuous film, producing an ADL. In recent years ADLs have been the subject of intensive theoretical [131][132][133][134][135] and experimental [105,[136][137][138][139][140][141] research activity, due to their potential application in magnonic devices such as high-sensitivity magnetic sensors, tunable filters or phase shifters [23,142,143]. In particular, ADLs have been found to behave as a network of interconnected magnonic waveguides, having an effective width equal to the distance between neighboring hole edges, where both localized and propagative SWs coexist.…”

Mapping the stray fields of a nanomagnet using spin qubits in SiC

“…By using state-of-the-art lithography techniques, magnetic nanostructures can be tailored such that the resulting magnetic dipolar field landscape locally affects the spin qubits. While isolated nanostructures act locally, they can also be built into periodic patterns such that the magnetic dipolar fields are repeated over a certain distance [8][9][10][11][12] . Importantly, patterning of nanomagnets also allows control over the dynamic magnetic excitations, or spin waves, opening the possibility to coherently control spin qubits at the low power consumption 13 limit, characteristic to spintronic and magnonic devices 14 .…”

Anisotropy engineering using exchange bias on antidot templates

“…A large asymmetry is obtained only when the applied field is off the high symmetry directions by a few degrees, with respect to the antidot lattice. The angular variation of the antidot modes in general is discussed elsewhere 29 for a different system. In order to understand the dipolar effects on the ferromagnetic resonance, we performed finite difference micromagnetic simulations using Mumax J/m, γ = 0.02).…”