Magnetostriction and Magnetic Microscopy Studies in Fe-Co-Si-B Thin Films

Abstract

This paper reports the effect of substrate temperature on the magnetostrictive behavior of sputtered Fe-Co-Si-B thin films. Magnetostriction measurements carried out by measuring the tip deflection in thin film cantilevers were found to increase with increase in substrate temperatures. To understand the variation of magnetostriction with substrate temperature, detailed structural, microstructural, magnetization and domain imaging studies were carried out. Magnetization studies indicated presence of strong in-plane magnetic anisotropy for all the films. The change in the in-plane coercivity with increase in substrate temperature was correlated with grain size and surface roughness effects. Angular dependent magnetic hysteresis and domain imaging studies carried out using longitudinal Magneto-optic Kerr microscopy displayed presence of strong in-plane uniaxial anisotropy for the as deposited film. Upon increase in substrate temperature, in-plane anisotropic nature was found to gradually change towards isotropic nature owing to the enhancement in crystallization and relaxation of stresses. The magnetization reversal along the in-plane easy axis and hard axis of magnetization was found to be dominated by domain wall motion and through a combination of coherent rotation, domain wall motion & rotation respectively. The increase in the magnetostriction with substrate temperature was correlated with the strong interplay between the crystallization, grain size and magnetic anisotropy.