M. Stampanoni

Effect of ion bombardment on the surface magnetism of Fe3O4

We have found that ion bombardment produces dramatic changes in the surface magnetism of Fe3O4. The surface layer with irregular magnetic behavior is more than 50 A thick. These findings are of importance for current studies of ferritelike sputtered thin films as well as magnetic alloys in general.

Different spin and lattice temperatures observed by spin‐polarized photoemission with picosecond laser pulses

The spin polarization of the photoelectrons emitted from Sn and Fe during picosecond (ps) and nanosecond (ns) laser pulses is measured as function of the laser intensity. For Sn the optically induced spin polarization is defined through the lattice symmetry. No difference is found between ps and ns heating. From this it is concluded that the melting of a metal like tin occurs on a time scale which is short compared to the duration of a 70 ps laser pulse. In Fe the spin polarization probes the magnetic order. It is found that Fe cannot be demagnetized within the duration of a 30 ps laser pulse, even if the melting point is reached in the laser focus. During a ns laser pulse the spin system and the lattice are in thermal equilibrium.

Ultrafast thermomagnetic writing processes in rare‐earth transition‐metal thin films

We use time‐resolved spin‐polarized photoemission to investigate thermomagnetic writing of domains in magneto‐optic media, focusing on the relaxation time of the magnetization and the dynamic behavior of the nucleation process. In our initial studies, we examine a 90‐nm‐thick GdTbFe film using a pulsed excimer laser (pulse duration: 16 ns) as the light source for the photoemission process. We find that the thermomagnetic switching behavior is different above and below the compensation temperature Tcomp. When the sample temperature is held above Tcomp, the spin polarization of the electrons emitted during the writing pulse has the sign of the initial state even though subsequent examination shows that a reversed magnetization domain has been formed. Therefore, the domain is thermomagnetically nucleated during the trailing edge of the 16 ns writing pulse or even later when the irradiated domain cools down. On the other hand, if the initial temperature is slightly below Tcomp, the electrons emitted during the writing pulse have reversed polarization showing that the reversal of the magnetization takes place quickly compared to the pulse duration. This difference shows that compensation‐point writing is much faster than Curie‐point writing. Based on these measurements we propose a model to interpret the different thermomagnetic switching processes which take place above and below Tcomp. The results can be explained by different thermal relaxation times between the excited electrons and the lattice and between the electrons and the spin system.We use time‐resolved spin‐polarized photoemission to investigate thermomagnetic writing of domains in magneto‐optic media, focusing on the relaxation time of the magnetization and the dynamic behavior of the nucleation process. In our initial studies, we examine a 90‐nm‐thick GdTbFe film using a pulsed excimer laser (pulse duration: 16 ns) as the light source for the photoemission process. We find that the thermomagnetic switching behavior is different above and below the compensation temperature Tcomp. When the sample temperature is held above Tcomp, the spin polarization of the electrons emitted during the writing pulse has the sign of the initial state even though subsequent examination shows that a reversed magnetization domain has been formed. Therefore, the domain is thermomagnetically nucleated during the trailing edge of the 16 ns writing pulse or even later when the irradiated domain cools down. On the other hand, if the initial temperature is slightly below Tcomp, the electrons emitted during th...

High‐speed magnetization reversal near the compensation temperature of amorphous GdTbFe

Using spin‐polarized photoemission with a pulsed laser as light source, it is shown that the time for a thermally induced magnetization reversal depends critically on the temperature of the sample. For amorphous GdTbFe the time is shorter (longer) than the duration of the 16 ns laser pulses if the initial temperature is below (above) the compensation temperature.

Magnetization reversal in a-GdTbFe investigated by time-resolved, spin-polarized photoemission

Abstract Pulsed laser induced, spin-polarized photoemission reveals that the magnetization reversal in a-GdTbFe films occurs in less than 1 ns if the sample is held below the compensation temperature (Tcomp). Above Tcomp the magnetization reversal time exceeds 16 ns.