HoFe$ _2$

As can be seen in Figure 6.3 the HoFe$ _2$ film has a markedly different Mössbauer spectrum compared to YFe$ _2$ and DyFe$ _2$. Unfortunately this may not be a pure HoFe$ _2$ spectrum as, due to the thinness of the sample layer, part of the spectrum will be recorded from the YFe$ _2$ seed layer.

Using the CEMS theory outlined in Section 2.5.2 an upper limit can be placed on the relative spectral contributions from the two layers. For a $ 500\ensuremath{\unskip\,\mathrm{\AA{}}}$ sample layer the ratio of sample to seed layer is $ 55\%$:$ 45\%$. Thus the spectrum is more akin to that from a HoFe$ _2$/YFe$ _2$ bilayer. Hence we cannot analyse the spectrum to give any accurate information about a HoFe$ _2$ thin film due to the overlap of the two sub-spectra and any possible interface effects.

In the $ 750\ensuremath{\unskip\,\mathrm{\AA{}}}$ DyFe$ _2$ thin film this ratio is $ 85\%$:$ 15\%$ giving a more representative spectrum of the sample layer. In the YFe$ _2$ thin film this effect does not apply as the sample and seed layer are the same material and continuous.

Dr John Bland, 15/03/2003