서강대학교

초록/요약 도움말

In high-density magnetic recording media, magnetically isolated grains are required to increase the signal-to-noise ratio (SNR). Carbon can be used to isolate FePt grains enabling their grain size smaller than 4.3 nm. Carbon atoms segregate to the boundaries during growth and provide an exchange-breaking layer, however, some other carbon atoms remain dissolved in the magnetic alloy. To identify the upper limit of carbon concentration in L1(0)-ordered (Fe0.5Pt0.5)(100-x)C-x, first-principles calculations are performed based on the density functional theory (DFT). The Brillouin function and Callen-Callen empirical relation determine the temperature-dependent magnetization and magneto-crystalline anisotropy energy enabling the determination of magnetic properties and Curie temperature required by 4 Tb/in(2) heat-assisted magnetic recording (HAMR) media and beyond. The calculated magnetization (Ms) of L1(0)-ordered (Fe0.5Pt0.5)(100-x)C-x decreases to 770 emu/cm(3) at x = 20 from 1030 emu/cm(3) at x = 0 at 300 K, and the magnetocrystalline anisotropy constant (Ku) to 2.05 MJ/m(3) at x = 20 from 15.48 MJ/m(3) at 300 K. It is striking to find that the Curie temperature (TC) increases to 728 K at x = 20 from 719 K at x = 0. Regardless of carbon concentration, the magnetic anisotropy direction is the out-of-plane. Combining Ms and Ku at 300 K with TC, the Ms- Ku-C concentration relation is plotted to guide the design of L1(0)-ordered Fe-Pt film for Tb/in(2) recording media. It is found that the upper limit of carbon concentration is determined to be about 12 at.% to retain Ms >= 800 emu/cm(3), TC >= 430 K, and Ku >= 5 MJ/m(3), which are necessary to achieve areal densities of 4 Tb/in(2) and beyond.