Stripes are Stars! Pt helps Fe to stay magnetized!

A. Enders, R. Skomski
Nebraska MRSEC
J. Honolka, K. Kern, K. Fauth, G. Schuetz
MPI Stuttgart, Germany
P. Varga
TU Vienna, Austria
H. Ebert
LMU Muenchen, Germany

The magnetic anisotropy energy is among the most important functional properties of magnetic elements. It determines the orientation and stability of the magnetization as well as the mechanisms and the dynamics of the magnetization reversal. New materials with extremely large anisotropy values are currently sought for the development of ultrahigh density magnetic recording media. As one example, FePt or CoPt alloys exhibiting L10 structure are currently in the focus of intensive research, as they were found to exhibit unprecedented anisotropy values. It was recently discovered that also atomically small nanostructures of Fe and Pt can, under certain conditions, exhibit magnetic anisotropy values similar to those of their L10 bulk counterparts. This discovery was possible after advances in nanostructure synthesis have been made to embed Fe atoms as monatomic Fe stripes or in other configurations into the surface of Pt single crystals. It was found that the Pt plays a critical role in the magnetism of these structures, as it dictates the structure’s magnetic anisotropy and thus helps the Fe to stay magnetized. Intriguingly, in the system studied, the interatomic exchange, magneto­crystalline anisotropy and Dzyaloshinski-Moriya interactions are all of the same order of magnitude, which leads to an interesting nanoscale interplay between ordinary magnetization states and noncollinear spin structures and hence to rather complex magnetic properties of the FePt nanostructures.