Magnetization reversal, damping properties and magnetic anisotropy of L 10-ordered FeNi thin films

Abstract

L 1 0-ordered magnetic alloys such as FePt, FePd, CoPt, and FeNi are well known for their large magnetocrystalline anisotropy. Among these, the L 1 0-FeNi alloy is an economically viable material for magnetic recording media because it does not contain rare earth and noble elements. In this work, L 1 0-FeNi films with three different strengths of anisotropy were fabricated by varying the deposition process in a molecular beam epitaxy system. We have investigated magnetization reversal along with domain imaging via a magneto-optic Kerr effect based microscope. It is found that in all three samples, the magnetization reversal happens via domain wall motion. Furthermore, ferromagnetic resonance spectroscopy was performed to evaluate the damping constant (α) and magnetic anisotropy. It was observed that the FeNi sample with a moderate strength of anisotropy exhibits a low value of α ∼ 4.9 × 10 - 3. In addition to this, it was found that the films possess a mixture of cubic and uniaxial anisotropies.