Influence of Ga+ milling on the spin waves modes in a Co2MnSi Heusler magnonic crystal

Abstract

Ferromagnetic resonance experiment was performed to study the magnonic modes of an antidot lattice nanopatterned in a sputtered Co2MnSi Heusler alloy thin film. The magnonic crystal was prepared with a Ga+ focused ion beam, and micromagnetic simulations were used to explain qualitatively and quantitatively the complex experimental spin waves spectrum. We demonstrate the necessity to consider the geometrical imperfections and the modification of the Co2MnSi magnetic parameters induced by the nanofabrication process to describe the evolution of the frequencies and spatial profiles of the principal experimental spin waves modes in the 0–300 mT magnetic field range. In particular, our model suggests that Ga+ milling induces a drastic decrease (between 80% and 90%) in the bulk Co2MnSi magnetic parameters. In addition, simulations reveal the presence of a diversity of localized and extended spin waves modes whose spatial profiles are closely related to the evolution of the magnetic state at equilibrium from a very non-collinear configuration up to a quasi-saturated state.