Reduction of macroscopic moment in ultrathin Fe films as the magnetic orientation changes

A study of the remanent magnetization ${\mathbf{M}}_{\mathit{r}}$ in ultrathin Fe films grown at 125 K on Cu(100) and Ag(100) substrates was conducted using spin-polarized secondary-electron spectroscopy. For bcc-Fe/Ag(100) and fcc-Fe/Cu(100) films, perpendicular ${\mathbf{M}}_{\mathit{r}}$ was observed for film thickness less than 7 and 11 Å, respectively. In-plane ${\mathbf{M}}_{\mathit{r}}$ was observed for thicker films. For thickness below the critical thickness, both systems showed a reversible switching transition of the magnetization orientation from perpendicular to in plane as the temperature was increased. For the Fe/Cu(100) films the switching could be observed for many temperature cycles providing that the film was not annealed above 350 K, while the Fe/Ag(100) films switching was stable for only 1–2 annealing cycles to 300 K. A loss of ${\mathbf{M}}_{\mathit{r}}$ during the switching transition is observed, and is attributed to a change in the magnetic nature of the film. The details of the loss of magnetization observed in Fe/Ag(100) and Fe/Cu(100) are significantly different.