Magnetic and transport properties of Fe-Au and Co-Au films

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Abstract
Thin film cobalt‐gold and iron‐gold alloys have been prepared by sputtering onto water cooled substrates. These alloys are crystalline with residual electrical resistivity (ρ) a factor of five greater than bulk alloys. For FexAu100−x the X‐ray diffraction patterns are characteristic of fcc structures (high Au content) and bcc structures (low Au content); CoxAu100−x shows mixed fcc and hexagonal diffraction patterns. Fe‐Au exhibits a constant magnetic moment per Fe of μB = 2.2 over the range 26 to 92% Fe. The resistivity of Fe‐Au at 4.2°K is about 40μΩcm and is independent of composition. The Hall effect expressed as Rs/ρ2 where Rs is the spontaneous Hall coefficient increases with Fe dilution. Co‐Au shows a concentration dependent magnetic moment which decreases with increasing Au and a Hall effect as given by Rs/ρ2 which increases in magnitude as the Co moment decreases. In addition the resistivity at 4.2 °K of Co‐Au is composition dependent increasing with decreasing Co content. The anisotropic magneto‐resistance in both Fe‐Au and Co‐Au behave similarly with the interesting feature that Δρ(Δρ = ρ∥−ρ⊥) has a maximum at about the same average magnetization as found for other alloys such as Ni‐Fe and Ni‐Co2. At the same composition of maximum Δρ the saturation magnetostriction becomes almost zero.