Magnetic Properties of L1₀ Fe-Ni-Pt Films for Heat Assisted Magnetic Recording

Abstract

Very high uniaxial anisotropy K_u as well as a moderate Curie temperature is required for magnetic materials by heat assisted magnetic recording (HAMR). Crystalline structure and magnetic properties of Fe-Ni-Pt thin films deposited on quarts glass substrates have been investigated in order to obtain optimum composition for the HAMR. L1₀ phase is found in Fe_60-xNi_xPt₄₀ (x = 0 to 24) with c-axis aligned in the perpendicular direction to the film plane. As Ni content x increases, the quality of (001) orientation is improved, while the order parameter S is gradually degraded. As a result, K_u in the perpendicular direction to the film plane is decreased from 3 x 10⁷ erg/cm³ for Fe₆₀Pt₄₀ to 1 x 10⁷ erg/cm³ for Fe₄₅Ni₁₅Pt₄₀ film. The Curie temperature measured is decreased with Ni content to 320°C for Fe₄₅Ni₁₅Pt₄₀. Thermal simulation on the Fe-Ni-Pt disk assuming the similar film structure as current perpendicular recording media has revealed that the temperature rise above 350°C is available by the laser irradiation with a power of 2 mW and pulse width of 2 ns. Therefore, Fe-Ni-Pt can be a candidate material with high anisotropy and optimum Curie temperature suitable for the HAMR.