Magnetic and conversion electron Mössbauer spectroscopy studies in Fe/Ta multilayers

We have prepared Fe/Ta multilayers by rf sputtering. A small 1-cm2 chip of 57Fe was placed on the Fe target. We studied the magnetization (M) and M-H loops and also carried out conversion electron Mössbauer spectroscopy (CEMS). The in-plane loops are rectangular with a lowest coercivity of 2.6 Oe. Magnetization studies indicate a dead Fe layer about 5 Å thick at each interface. CEMS spectra for samples with t(Fe)≥54 Å showed a typical six-line pattern, indicating the presence of bulk Fe. No other Fe sites could be detected. However, for t(Fe)=24 Å, where almost 50% of Fe is nonmagnetic, CEMS spectra showed the presence of a strong paramagnetic doublet.