SPIN RESONANCES IN AMORPHOUS-Y-FE ALLOYS

We present spin resonance measurements on amorphous Y1-xFex alloys using both bulk (a-YFe2) and thin film (x = 0.70, 0.77, 0.83) samples. At 300 K, in every sample, we have found one strong line (S1) whose frequency and angular dependances imply that it is a uniform mode ferromagnetic resonance in a very thin (≈20-40 nm) surface layer. Previous static measurements indicate that these alloys have no long range order at 300 K. The effective magnetization of the surface layer is a non-monotonic function of the Fe content. Rutherford back scattering experiments on bulk samples are used to demonstrate that there is no significant variation in composition, with depth. We show that S1 cannot be attributed to segregation, surface contamination or crystallinity. We propose that the surface layer is another amorphous phase of the alloy. A second resonance (S3) has been ascribed to some of the superparamagnetic spin clusters known to be present in these systems. As reported earlier, we observe other resonances whose origin is not fully understood. © 1979.