GMR Results

Figure: Percentage change in resistance under an applied field for the $\left[\mathrm{Ce}(20\,\mathrm{\AA{}})/\mathrm{Fe}(17\,\mathrm{\AA{}})\right]_{60}$ sample.

GMR data was taken on some of the Ce/Fe samples studied in this thesis by A. Mohamed[37]. All samples studied at room temperature showed no significant change in resistance under an applied magnetic field.

One sample, $\left[\mathrm{Ce}(20\,\mathrm{\AA{}})/\mathrm{Fe}(17\,\mathrm{\AA{}})\right]_{60}$, was studied at $77\ensuremath{\unskip\,\mathrm{K}}$ and this data is plotted in Figure 7.6. A reduction in resistance from the zero field state is seen as the field is applied in the positive or negative direction. A quadratic fit is included as a guide for the eye.

This result is typical of the GMR effect in antiferromagnetically coupled multilayers.[40] This correlates with the typical antiferromagnetic temperature dependence seen for this sample in Figure 7.1. The SQUID data shows the sample has a $T_{N} = 160\pm5\ensuremath{\unskip\,\mathrm{K}}$, placing the $77\ensuremath{\unskip\,\mathrm{K}}$ GMR measurement within the antiferromagnetic region.