Magnetic bubble domain phase at the spin reorientation transition of ultrathin Fe/Ni/Cu(001) film.

Magnetic domain phases of ultrathin Fe/Ni/Cu(001) are studied using photoemission electron microscopy at the spin reorientation transition (SRT). We observe a new magnetic phase of bubble domains within a narrow SRT region after applying a nearly in-plane magnetic field pulse to the sample. By applying the magnetic field pulse along different directions, we find that the bubble domain phase exists only if the magnetic field direction is less than approximately 10 degrees relative to the sample surface. A temperature dependent measurement shows that the bubble domain phase becomes unstable above 370 K.