Effects of Ta Buffer Layer on Structural and Magnetic Properties of Sputtered Ni2FeAl

Abstract

In the present investigation, we report the growth of off-stoichiometric Ni-based Heusler thin films of different thicknesses (6–30 nm) on a Si (100) substrate by radio frequency sputtering at 300 °C. We have used an indigenously prepared target comprising thin sheets of Ni, Fe, and Al in specific proportions. Of all the Heusler alloys, Ni₂FeAl is the least researched alloy that may offer immense possibilities in developing spin-based devices. The Ni₅₅Fe₁₄Al₃₁ films crystallize into the A2 phase as confirmed by the diffraction pattern. With the increase in the thickness of films, surface roughness improves followed by an increase in saturation magnetization (M_S). Further, we have explored the effect of Ta buffer on the static and dynamic magnetic behavior of films and compared it with unbuffered films. The Ta buffer layer significantly impacts the surface morphology of the films. The in-plane magnetic hysteresis loops indicate higher M_S with Ta buffer. Dynamic magnetization is probed via ferromagnetic resonance technique over a broad band of microwave frequencies and has been quantified in terms of Gilbert damping constant (α). The Ta buffer reduces the Gilbert damping constant from 10.1 × 10⁻³ to 8.4 × 10⁻³ in 30 nm thick films.