(001) Oriented $L1_{0}$ FeCuPt for Heat-Assisted Magnetic Recording*

High magnetic anisotropy materials are critical to key technologies such as ultrahigh density magnetic recording and permanent magnets. Among them, ordered FePt alloys in the $L$1$_{0}$ phase are particularly sought after, for the emerging heat-assisted magnetic recording (HAMR) media. However, the highly desirable properties are associated with the tetragonal $L$1$_{0}$ phase. Key challenges exist in the high annealing temperature necessary to transform the as-deposited disordered cubic $A$1 phase into the ordered tetragonal$ L$1$_{0}$ phase and the ability to maintain the magnetic easy axis perpendicular to the film. We have achieved (001) oriented $L$1$_{0}$ FeCuPt thin films, with magnetic anisotropy up to 3.6 x 10$^{7}$ erg/cm$^{3}$, using atomic-scale multilayer sputtering and rapid thermal annealing (RTA) at 400 $^{\circ}$C for 10 seconds, which is much more benign compared to earlier studies [1]. The artificial ordering in the multilayer structure and a significant tensile stress exerted by the underlying Si/SiO$_{2}$ during RTA facilitate the formation of (001) oriented $L$1$_{0}$ phase. The $A$1 to $ L$1$_{0}$ phase transformation has been investigated by x-ray diffraction and the first-order reversal curve (FORC) method [2]. The $L$1$_{0}$ ordering takes place via a nucleation-and-growth mode. Traditional x-ray diffraction is not always reliable in generating a true order parameter, due to non-ideal crystallinity of the $A$1 phase in some of the samples. A magnetization-based $L$1$_{0}$ phase fraction is extracted, providing a quantitative measure of the $L$1$_{0}$ phase homogeneity [3]. \\[4pt] [1] D. A. Gilbert, L. W. Wang, T. J. Klemmer, J. U. Thiele, C. H. Lai, and K. Liu, \textit{Appl. Phys. Lett.}, \textbf{102}, 132406, (2013).\\[0pt] [2] D. A. Gilbert, G. T. Zimanyi, R. K. Dumas, M. Winklhofer, A. Gomez, N. Eibagi, J. L. Vicent, and K. Liu, \textit{Sci. Rep}, \textbf{4}, 4204 (2014).\\[0pt] [3] D. A. Gilbert, J. W. Liao, L. W. Wang, J. W. Lau, T. J. Klemmer, J. U. Thiele, C. H. Lai, and K. Liu, \textit{APL Mater}, \textbf{2}, 086106 (2014).