Magnetic properties of Fe62Co19Ga19 films deposited on Si(100) substrates

Abstract

Fe81–XCoXGa19 films, with x = 0−23 atom % Co, were deposited on Si(100) substrates, respectively, by the dc magnetron sputtering method. Film thickness (tf) ranged from 30 to 400 nm. We have done the following experiments on those films: saturation magnetostriction (λS), high-temperature magnetic hysteresis, x-ray diffraction (XRD), atomic force microscopy, Auger-depth profile analysis, and plane-view and/or cross-section transmission electron microscopy. Our main finding is that if x increases from 0 to 19 atom % Co, λS increases from 56 to 152 ppm, and if x continues to increase from 19 to 23 atom % Co, λS decreases. These results indicate that the addition of Co in the Fe81Ga19 alloy is advantageous in enhancing λS, if x is the correct value. From XRD, the Fe62Co19Ga19/Si(100) film comprises the A2 and B2 phases. The mechanism for large enhancement of λS in Fe62Co19Ga19/Si(100) is related to an intrinsic origin. The tf dependence of λS for the Fe62Co19Ga19 films is that: [1] in the range of 110 ≤ tf ≤ 400 nm, λS increases as tf decreases; [2] in the range of 30 ≤ tf ≤ 110 nm, λS decreases as tf continues to decrease. The λS behavior in the regions [1] and [2] is explained based on the modified Neel model. Other physical properties of the Fe62Co19Ga19 films include the following: saturation magnetization 4πMS = 1.8 – 2.0 T, coercivity HC = 35 – 64 Oe, Curie temperature TC = 597 °C, planar (mean) grain size DP = 29.6 nm, and columnar grain size DL ≈ tf.