Critical spin fluctuations and Curie temperatures of ultrathin Ni films on W(110): A magnetic-resonance study in UHV
Recently it has been demonstrated that para- /l/ and ferromagnetic resonance /2/ can be performed in situ on well-characterized magnetic monolayers in UHV. The magnetic properties of 3d mono- and multilayers have been studied deep in the ferromagnetic phase and valuable information on the thickness dependence of the magnetic anisotropy in these films was obtained. We focus on the magnetic properties near the phase transition. In this regime magnetic quantities, such as the static susceptibility χ0 and the spontaneous magnetization Msp, follow a power law with respect to the reduced temperature T-Tc/Tc. For Gd mono- and multilayers on W (110), we were able to determine the Curie temperatures TC(d) and the critical exponent 7 of χ0(T>TC) as a function of film thickness d /l/. Critical broadening of the EPR linewidth has been observed in bulk ferromagnets near TC. In the case of bulk Ni only one /3/ of numerous magnetic resonance experiments showed a resonance like broadening when approaching TC (630 K) from below and also from above. The figure below shows the broadening, due to spin fluctuations, for Ni-films in UHV. The result of the present work is to show that epitaxial films grown under controlled conditions in UHV are “more perfect” solids than previously used bulk materials.
- /4/.Yi Li, M. Farle, K. Baberschke, Phys. Rev. B41, May 1 (1990)Google Scholar