Abstract
Magnetic relaxation of FePd alloy epitaxial thin films with very flat surfaces prepared on MgO(001) substrate are measured by in-plane broadband ferromagnetic resonance (FMR). Magnetic relaxation is investigated as Δω for FMR absorption peak by frequency sweep measurements. ΔH is calculated by using the measured Δω. Gilbert damping constant, α, is estimated by employing a straight line fitting of the resonant frequency dependence of ΔH. The α value for an FePd film deposited at 200 ˚C, which shows disordered A1 structure, is 0.010 and ΔH0, which is frequency independent part of ΔH, is 10 Oe. The α value for a film annealed at 400 ˚C, which shows partially L10 ordered structure (S=0.32), is 0.013, which is slightly larger than that for the disorder A1 structure film. However, ΔH0 for the annealed film is 85 Oe, which is much larger than that for the film with disordered structure. The results show that the magnetic relaxation of the 400 ˚C annealed film is mainly dominated by ΔH0, which is related with magnetic in-homogeneity caused by the appearance of perpendicular anisotropy of partially ordered phase.
Highlights
Spin-transfer switching is an attractive technique to deduce the electronic current for switching the magnetization direction of a magnetic element in devices like perpendicularly magnetized magnetoresistance random access memory (PMRAM) [1, 2]
Very flat surfaces are realized for the FePd films prepared by employing the two-step process
The results suggest that the magnetic relaxation of partially L10 ordered FePd film with perpendicular anisotropy is mainly dominated by 0 which is caused by magnetic in-homogeneity in the film
Summary
Spin-transfer switching is an attractive technique to deduce the electronic current for switching the magnetization direction of a magnetic element in devices like perpendicularly magnetized magnetoresistance random access memory (PMRAM) [1, 2]. For PMRAM devices, perpendicularly magnetized magnetic thin films with small Gilbert damping constant, , are required [1]. An L10 ordered FePd alloy epitaxial thin film is one of candidate materials. Ferromagnetic resonance (FMR) is a powerful method in studying Gilbert damping constant, of magnetic thin film. There are a few FMR studies of epitaxial FePd thin films with perpendicular magnetic anisotropy [3, 4]. Gilbert damping constant is estimated for Fe50Pd50 Very flat surface is required in FMR measurements to evaluate intrinsic magnetic relaxation in order to avoid extrinsic effect by surface roughness [7]. A difference in the magnetic relaxation between FePd films with a disordered A1 structure and with a partially ordered L10 structure is discussed
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