An investigation of the effect of structural order on magnetostriction and magnetic behavior of Fe-Ga alloy thin films

This paper reports results from a comprehensive study of Fe-Ga films fabricated over a wide range of growth conditions. Polycrystalline Fe100-xGax films (14 <= x <= 32) were deposited (using three different combinations of growth parameters) on Si(1 0 0)using a co-sputtering and evaporation technique. The growth parameters (sputter power, Ga evaporation rate and chamber pressure) were used primarily to control the Fe:Ga ratio in the films. X-ray diffraction showed that all films had < 1 1 0 > crystallographic texture normal to the film plane. The lattice parameter increased with % Ga up to x = 22 and was independent of growth parameters. Conversion electron Mossbauer spectroscopy studies showed a predominance of the disordered A2 phase in all films. It appears that the use of vacuum deposition with appropriate parameters can effectively suppress the D0(3) ordered phase. Systematic studies of the effective magnetostriction constant as a function of composition support this conclusion. It was found that films of high effective saturation magnetostriction constant and low stress could be fabricated using low Ar pressure, irrespective of sputter power or evaporation rate, giving properties useful for application in microelectromechanical systems. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.