In search of systems that show perpendicular magnetism in the last two decades a large number of experimental studies was published in which the magnetic properties of finite films of Fe, Co or Ni on noble metal substrates were investigated. It turned out that in quite a few cases the experimental set-ups had to be improved considerably in order to produce laboratoryindependent results. There were (are) even a few systems that gave rise to heated discussions concerning the reported findings. Most prominently in this respect were (are?) the systems Ni and Fe on Cu(100), since not only the kind of deposition mattered, but also the concentration of remaining gases in the high vacuum chamber was (is) of crucial importance. In particular layer relaxation at and in surface near regions seemed to dependent strongly on growth and vacuum conditions. In the following, first two kinds of systems, namely Fen/Au(100) and Com/
Nin/Cu(100), are chosen in order to illustrate a very important property of magnetically coated surface, the so-called reorientation transition, which occurs at some materials-dependent critical thickness. The first example is shown because later in Chapter 18 this system will be discussed again in terms of ab-initio magneto-optics, i.e., in terms of theoretical concepts describing the actually measured quantities. The second system, which in fact shows
two reorientation transitions, serves to introduce the concept of layer-resolved quantities, which turned out to be extremely useful not only for the interpretation of experimentally determined magnetic anisotropy constants but also for related properties such as electric transport.