Effect of Thickness and Deposition Rate on the Structural and Magnetic Properties of Evaporated Fe/Al Thin Films

We report experimental results on the structural and magnetic properties of Fe thin films deposited by thermal evaporation onto polycrystalline Al substrates. The effect of thickness t (in the 76 to 431 nm range) and deposition rate are investigated. The texture, the strain, and the grain size values were derived from X-ray diffraction (XRD) experiments. The thinner film (76 nm) has no texture, while all other samples have a < 110 > texture. The strain values epsilon are small and negative (compressive stress) and equal to -0.1 % for films with t less than 100 nm, it decreases (in absolute value) to -0.07 % and then remains constant for t greater than 100 nm. The grain size values D are found to be between 44 and 73 nm. The grain size decreases with increasing deposition rate regardless of t. Hysteresis curves, inferred from the vibrating sample magnetometer (VSM), show an in-plane magnetic anisotropy for all samples. The squareness S increases and the coercive field H (C) decreases with increasing D up to D = 55 nm, then they remain constant beyond this grain size value. Higher deposition rates led to smaller grain, smaller remnant magnetization, and higher coercive field. For t = 99 nm, the decrease of the temperature T from room temperature to -130 A degrees C led to 20 and 5 % increases in H (C) and S, respectively.