Composite media with reduced write temperature for heat assisted magnetic recording

Highlights: • Reducing write and heat spot temperatures is beneficial to Magnetic Recording. • An ECC media: T_c (write layer) = 600 K; T_c (storage layer) = 500 K is the proposed solution. • This reduces write temperature from 738 K to 486 K, a very important improvement. • The proposed media has a performance similar to that of previously developed media. • Recording performance degrades if storage layer anisotropy decreases below a limit. -- Abstract: A major issue plaguing Heat Assisted Magnetic Recording (HAMR) is the high writing (T_write) and peak heat spot temperatures (T_peak). To counter this, a low temperature thermal exchange coupled composite (ECC) media with reduced write temperature relative to previous high temperature thermal ECC media is introduced. The FePt T_c is reduced from 700 K to 500 K, and the write layer T_c is reduced from 900 K to 600 K. Optimizations for M_s and K_u of the write layer generate values of M_s = 700 emu/cm³ and K_u = 1.0 × 10⁷ erg/cm³ at 300 K. Switching Probability Distribution (SPD) calculations with lowered T_peak = 650 K indicate T_write = 487 K. This indicates a T_write reduction by 34% as compared to the previous write temperature of 738 K for the high temperature thermal ECC media. Examining the FWHM of the SPD under 0% and 3% T_c variation indicates a noise reduction of ∼20% relative to single layer high T_c FePt media, and a much larger reduction relative to low T_c FePt media. The jitter values at lowered T_c approach the ideal value set by the grain size in the absence of any T_c and K_u variation. Simulations with uncorrelated and correlated T_c and K_u variations in the write and FePt layer generate similar results. Reduction of FePt T_c may reduce the anisotropy relative to its undoped value: reduction of anisotropy by 33% is found to adversely affect the SPD by only 3–4%, but has a larger impact on jitter. These results help establish the usefulness of a low temperature thermal exchange coupled composite media for HAMR.