Tuning static and dynamic properties of FeGa/NiFe heterostructures

Abstract

In this work, the frequency-dependent magnetic properties of sputtered Galfenol/Permalloy (Fe85Ga15/Ni81Fe19 or FeGa/NiFe) magnetic multilayers were examined to tailor their magnetic softness, loss at microwave frequencies, permeability, and magnetoelasticity, leveraging the magnetic softness and low loss of NiFe and the high saturation magnetostriction (λs) and magnetization (MS) of FeGa. The total volume of each material and their ratio were kept constant, and the number of alternating layers was increased (with decreasing individual layer thickness) to assess the role of increasing interfaces in these magnetic heterostructures. A systematic change was observed as the number of bilayers or interfaces increases: a seven-bilayer structure results in an 88% reduction in coercivity and a 55% reduction in ferromagnetic resonance linewidth at the X-band compared to a single phase FeGa film, while maintaining a high relative permeability of 700. The magnetostriction was slightly reduced by the addition of NiFe but was still maintained at up to 67% that of single phase FeGa. The tunability of these magnetic heterostructures makes them excellent candidates for RF magnetic applications requiring strong magnetoelastic coupling and low loss.