| Résumé | We determined the temperature dependence of the magnetization of thin Au97Fe3 films in the thickness range between 1 and 50 nm by performing polarized neutron reflectivity measurements in a magnetic field of 6 T in a temperature range from 200 down to 2 K. For the films in the thickness range from 50 to 2 nm, we observed a Brillouin-type behavior of noninteracting Fe atoms down to 50 K followed by a strong reduction compared to the Brillouin curve below 50 K. This reduction in the magnetization is a measure of the spin glass frustration and depends on the film thickness below 20 nm as shown in our previous study [M. Saoudi, H. Fritzsche, G. J. Nieuwenhuys, and M. B. S. Hesselberth, Phys. Rev. Lett. 100, 057204 (2008)] on Au₉₇Fe₃ films. The present study is a continuation of this work extending the thickness range down to 1 nm. It shows that below 10 nm, the reduction in the spin glass magnetization compared to a Brillouin-type behavior decreases with decreasing film thickness. Finally, the magnetization of the 1-nm-thick film could be described with a Brillouin function also below 50 K proving that ultrathin Au₉₇Fe₃ layers below 1 nm do not show spin glass behavior anymore but are paramagnetic. |
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