Many experiments, such as optical, superconductivity, etc, use the samples that involve rare earth metals and transition metals. Why are they used that often. Is the main reasons:
- They have the required electronic structure in its d- and f- orbital so that we can create the required spin-spin interaction.
- They provide the required structure of the crystal
- They provide the required energy band gap
Edit: Here the samples I mean is the usual YBCO, or some papers, say Gd5Si2Ge2, that I do not have any idea. I am also curious about why they decide to investigate a particular compound in the first place?