Fig. 4: Graded CoFeB magnonic channels.
From: Two-dimensional gradients in magnetic properties created with direct-write laser annealing
a Top-down view of a CoFeB/MgO film containing multiple 3 μm-wide stripes with linear magnetic anisotropy gradients written over a large area of 3 mm × 3 mm. b Spin wave dispersion of the patterned film from mumax3 simulations. The white dashed line indicates the dispersion of the as-grown film. c Spin wave dispersion of the patterned film from k-resolved BLS measurements. A 3.5 GHz band of allowed frequencies is observed for the patterned film at all applied magnetic fields (indicated by the white arrow in the top panel). With an applied magnetic field of μ0H = 0.22 T, 6 GHz – 9.5 GHz is allowed (top panel). As the field increases to 0.26 T, the frequency band shifts to 7.3 GHz – 10.8 GHz (middle panel), and then to 9.8 GHz – 13.3 GHz at μ0H = 0.35 T (lower panel). d Out-of-plane ferromagnetic resonance linewidth μ0ΔHFMR vs frequency f for an as-grown and annealed film. The Gilbert damping (proportional to the slope of the linear relationship between linewidth and frequency) is comparable for the as-grown and annealed film. Error bars indicate the standard deviation of the linewidth from fitting the data (see “Magnetic characterization”).
