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

Fe81-XCoXGa19 films, with x = 0 23 atom % Co, were deposited on Si(100) substrates, respectively, by the dc magnetron sputtering method. Film thickness (t(f)) ranged from 30 to 400 nm. We have done the following experiments on those films: saturation magnetostriction (lambda(S)), 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, lambda(S) increases from 56 to 152 ppm, and if x continues to increase from 19 to 23 atom % Co, lambda(S) decreases. These results indicate that the addition of Co in the Fe81Ga19 alloy is advantageous in enhancing lambda(S), 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 lambda(S) in Fe62Co19Ga19/Si(100) is related to an intrinsic origin. The tf dependence of lambda(S) for the Fe62Co19Ga19 films is that: [1] in the range of 110 <= t(f) <= 400 nm, lambda(S) increases as t(f) decreases; [2] in the range of 30 <= t(f) <= 110 nm, lambda(S) decreases as t(f) continues to decrease. The lambda(S) 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 4 pi MS = 1.8 - 2.0 T, coercivity H-C = 35 - 64 Oe, Curie temperature T-C = 597 degrees C, planar (mean) grain size D-P = 29.6 nm, and columnar grain size D-L approximate to t(f). (C) 2011 American Institute of Physics. [doi: 10.1063/1.3553768]